I think the whole thing of "people don't play older games" is less a case of not wanting to (or at least not willing to) and more a case of friction.
If I can have an add-on to my PS Plus that gives me access to download (or stream) a whole three generations of classic titles just as easily as PS4/PS5 games. Then I'd probably dabble in it and it'd expand from there; and I say that as someone who's usually much more into the future and the next big thing on the horizon. I know we basically have this already, but it's clunky and poorly populated, I think it could be sooo much better.
I think this would be especially true for [fingers-crossed] a future handheld, people are more accepting of the generally more rudimentary experiences of older generations such as PS1/PS2 on a handheld.
You just need to put the option right in front of someone and give them a nudge; and make it as easy as possible to get stuck in. Of course, not everyone will be into it, but I think a more significant number than people expect would be willing to jump in if it's made as easy as possible and if it works really well.
I've been meaning to play Silent Hill 1, 2 & 3 but I've gone over the options and I've decided I want to play them in their original PS form (the PC and other versions just look wrong to me, the softer, more cohesive presentation of the originals looks more fitting). So I now have to get a PS2 and the discs. But, I'd much rather play them on my PS5 Pro when I get it, perhaps with some filter options and a locked framerate. And I'd be happy to pay $5-10 a pop for digital versions or subscribe to a PS Plus add-on for them.
Disc support would be nice too, as not all games will be available due to licensing and some people already have a collection. I know this isn't monetisable in that way but it's unlikely to put much of a dent in things as digital would be the main way people consume these older games. Of course, Sony dropped the CD laser from PS4 & current PS5, so they can't even play those games on disc if they wanted to -- probably saved them a thruppence ha' penny on bom.
I find it hard to believe Sony can't do near-flawless PS1/PS2 emulation at this point and monetise it. PS3 would be more difficult but I'm still having a hard time buying the possibility that they can't do it (alternatively, as I've said before, what about making an absolutely miniscule CELL on a modern process node to put in future consoles [they're gonna have to update those streaming servers at some point or another too, strung together PS3 boards are only gonna last so long]).
I also think PS Plus should go modular with more granular options so that people can build their own package with a variety of specific "tick-box" options. Among them in this context would be a PS1/PS2 package, a PS3 package & a PSP/PSVita package, just a few dollars each extra a/mth.
To have access to a full back catalogue at this point I'd need a PS2, a PS3, a PS5 & a PSVita. Also, for VR I need both a PSVR (with its clunky break out box, an adapter, Move controllers & a PS4 Camera), and a PSVR2. Add in standard controllers, select accessories and cables/connections. It's a total mess..