It’s 6:30 p.m. at Jimmy’s Steer House in Arlington. A gray-haired waitress hustles across the dining room clutching a neon-green margarita that looks like a birdbath — a deal at $6.99. “They’re good,” she says out of the side of her mouth to a gawking table, not missing a step. Another group of waitresses huddles around a booth, toting strawberry shortcake topped with flickering candles.

“Happy birthday, dear Joan!” they croon. The room breaks into applause. Joan looks delighted.

One of those servers, Donna Grenier, has been here for 31 years. She’s modest, though.

“Some girls have been here even longer. There’s no better place to work,” she says. “The customers, the owners — we’re a little family.”

In a corner near the entrance, Medford’s Terese Brennan and her husband, Robert Minichiello, tuck into dinner. He’s 90, a retired fireman. She’s 84, a self-described “all-around broad.” They used to go out dancing and bowling every week. Now, they come to Jimmy’s.

“I could come here every Sunday! Why go anywhere else?” Brennan says to her husband, hoisting a glass of red wine on ice. (“Everything in moderation,” she says.) They eat here after good medical news. They ate here when her son retired from the military.

It’s not fancy. Instead of craft cocktails, there are red buttons on every server’s shirt stating, “WE ID UNDER 21.” The menu is simple: broiled scrod, crabmeat pie blanketed with buttery cracker crumbs, plastic tubs of Russian dressing served alongside towers of iceberg.

There are hundreds of such places across Massachusetts — you know the ones. Some still exist; some persist only in our memories, the type of places that families across the land would visit every Sunday for respectable relish trays and desserts wheeled on carts.

Most of these places don’t employ publicists. They lack a strong social media presence. Many patrons are grandmas, not Instagrammers. Farm-to-table, small plates, molecular gastronomy, fusion, cat cafes — some trends fizzle; others endure. Yet these stalwarts soldier on unchanged, many for generations and often beneath the radar, buoyed only by good will, loyalty, and nostalgia.

A recent post about such restaurants on Boston’s popular Hidden Restaurants message board, run by local restaurant wag Marc Hurwitz (full disclosure: this anthropological research was instigated by me), yielded floods of recommendations. The Continental in Saugus! Greg’s in Watertown! Frank’s Steakhouse in Cambridge! The Winthrop Arms in Winthrop! Good Thymes in Lowell!

Take Good Thymes: This is a hangout for Lowellians of a certain age, the type of place where older couples chat after church and grandchildren gamely dine with grandparents in squeaky-clean coral booths. Oldies warble on the stereo. Homemade pies glisten in cases near the front door. Sweet-and-sour chicken is the most exotic thing on the menu. It’s across from a cemetery — the jokes write themselves. But the packed dining room would be the envy of many restaurant owners. What’s the trick?

“We found a niche,” says Jim Boutin, who began his culinary career as a dishwasher at a Boy Scout camp. “Our customers dictated to us what they wanted to eat, and we did it. When we opened, we had sandwiches and burgers. Our customers said, ‘We want meat loaf. Can you make meat loaf?’ Yeah, I can make that. They wanted croquettes. Yeah, I’ll make croquettes. I thought, ‘Geez, I guess our menu is absolutely useless.’ We turned around and made a different one, catered to them. We followed the need because that’s what they wanted, and we all became good friends.”

Two of his best customers are Peggy Lally and her son, Michael. They share a multifamily home around the corner from Good Thymes; he’s upstairs, she’s downstairs. At 92, she still drives — and sometimes goes out alone with “the girls” — but he looks after her. His father is dead, and so he keeps her company every afternoon at 4 p.m. at their regular table. It’s an important gathering place since their local parish, Sacred Heart, has closed. They chat, greet friends and their favorite servers, and catch up on the day’s gossip.

“By the time we get to our table, my mother’s water with two lemons is on the table, and so is my Crown and ginger. Sometimes we’ll say, ‘Jim, put this on the menu.’ Being a regular has its perks,” he says, laughing.

In an era of celebrity chefdom, no culinary egos here. In recent years, chefs have been criticized for feuding with customers on Yelp or social media, refusing substitutions, or treating restaurants solely as creative showcases as opposed to bastions of hospitality.

Boutin takes a different approach, one that he says is the secret to his success. He knows his audience. His particular clientele isn’t looking for culinary innovation. They want fresh, homemade food. That’s it.

“It’s simple food. No chemicals. It’s real — real mashed potatoes that someone mashed and peeled, all day long,” Boutin says. “Our customers have nothing to prove, and neither do we. They’re just good, honest people.”

David Gall, who runs the venerable Winthrop Arms in Winthrop, known for seafood, chicken pie, and free weekend valet service, is more succinct when discussing his endurance. “It’s ‘keep it simple, stupid.’ It’s not gourmet food. It’s real good, comfort food,” he says.

It’s also about service, says Tony Karapatsas, head of the Burlington-based American Food Systems. The group oversees family-friendly mainstays like Jimmy’s Steer House in Arlington and Saugus, Grassfields in Andover and Waltham, and Mario’s in Lexington, which turned 45 last summer. Karapatsas started with the restaurant group as a dishwasher at 17.

“I tell my managers that I want to be the L.L. Bean of restaurants,” Karapatsas says. “If you go to L.L. Bean, no matter what you ask, they say ‘yes’ with a smile. I want to say ‘yes’ to everything that the customer asks and to make sure, when they leave, they’re happy. If we get a complaint on a server, we sit down and figure out: How can we get that server to think like us? The customer is doing us a favor. We’re not doing them a favor.”