Romance has always been the force that drives the PBS period drama “Downton Abbey.” This season’s most sizzling storyline wasn’t about widowed Mary Crawley’s (Michelle Dockery) secret getaway with a potential new spouse, but the surprisingly lively love lives of her grandmother, Violet (Maggie Smith), and mother-in-law, Isobel (Penelope Wilton).

“I think people have emotional lives until they, on the whole, die or at least get too old to care,” says “Downton” creator and writer Julian Fellowes. “I don’t see why a woman like Isobel Crawley, who has been widowed quite young and is still certainly in late middle age — the idea that it would be not be appropriate to have any love interest is something I just don’t understand. We all know these (older, single) women in our own lives … they’re still capable of a romantic story, they’re still capable of a relationship. To say they’re not is to say everything’s hopeless once you hit 40.”

Perhaps in part because of the influx in quality television and the opportunities that arise from it, recent years have seen a surge of seasoned veteran actors hitting the smallscreen in much meatier roles than usual. “Downton” may be the prime example with Smith’s (en)titled aristocrat famously uttering scene-stealers like “What is a weekend?” (and scoring her two Emmys in the process), but it’s certainly not alone.

This season has given us Cicely Tyson dispensing tough love on ABC’s “How to Get Away With Murder”; “Orange Is the New Black’s” posse of senior citizens stealing the show on Netflix; Jon Voight chewing scenery in Showtime’s “Ray Donovan”; Billy Crystal returning to TV as an established actor named Billy Crystal looking for a comeback in FX’s “The Comedians”; Jeffrey Tambor’s seventysomething parent embracing her transgender truth in Amazon’s “Transparent”; Ivonne Coll stealing scenes as an abuela as beloved as she is devout on CW’s “Jane the Virgin,” and many, many others.

As the showrunners for FX’s Reagan-era drama “The Americans,” Joe Weisberg and Joel Fields not only employ Margo Martindale as a handler who, for a while, had the unfortunate nickname of “Granny,” but this year welcomed Frank Langella as her former paramour and Lois Smith in a powerfully nuanced guest turn as an ill-fated office worker. Weisberg and Fields love that these actors can not only remember the cultural climate of the time in which their show is set, but add to its accuracy. And, unlike “The Americans’” younger actors, they know how to dial a rotary phone.

And then there are the rare shows where the entire focus is on more mature characters, such as Marta Kauffman and Howard J. Morris’ new Netflix series “Grace and Frankie.” The comedy stars Jane Fonda and Lily Tomlin as frenemies who find common ground when their law partner husbands, played by Martin Sheen and Sam Waterston, leave the women for each other.

“We wanted to do something about their age; about this — especially for women — marginalized time in your life. This is a huge segment in our population,” Kauffman says. The show has a personal connection for her. “Hovering around 60, I’m very interested in the way our lives change — especially for women post-menopause — and what happens to us physically and emotionally.”

Fellowes agrees. Although much of “Downton’s” earlier plot lines revolved around the patriarchal obsession with securing a male heir, he says “women determine the nature of the family more than anyone else and if you want to do a drama about a family, you must have important roles for women.

“What I’ve never understood about a lot of television drama is that everyone would agree with you about older men — there’s never been a shortage of older men in anything — but it’s women who have been short-changed. You might get the one matriarchal figure and everyone else is gorgeous and 28.”

Bill Newcott, AARP magazine’s features editor and founder of the organization’s Movies for Grownups, says these casting decisions make good business sense. After all, it’s the older demographic that still has appointment TV.

There’s “a hunger for our audience to see people in those age groups play essential roles,” he says.

Kauffman points out that her show, and most of the others mentioned, appear on cable or digital channels.

“When you go outside of network, especially with something like Netflix, there’s an opportunity for everyone to find something that they want to watch,” she says.

But Newcott sees a foundation in network TV’s obsession with procedural dramas.

“The format that calls for a strong central person who is barking the orders and that people come to with their problems is a great place to put someone who commands authority on the screen. And that, by cultural conditioning, means it’s going to be an older character.”

All the more reason to celebrate William Petersen’s return to CBS for the grand finale of “CSI.”