Yes, several generations ago. Times haved changed. We are have entered an age where carrying over stats (trophies, saved data, friendslist, subscriptions, ext) is factor in deciding where to go next and that is just not exclusive to video games. In the yesterdays when you bought a new phone, you essentially had to re add numbers/ apps manually, now assuming you stick with your service they will transfer everything for you. People like that. That keeps people. Those people are also gamers. Gaming is not dominated by dwebs anymore, hell "gamer" does not even have the negative connotation associated with it anymore. Those gamers outnumber Internet gamers. If we have people who would stick to the same phone services for convenience, why would that changed in regards to consoles? It's not brand loyalty in regards to the normal definition but more like convenience loyalty, " I got all these games, all these trophies, all the friends, put all this money into this account .. why not get a PS5?". It is not because "I love Sony!" but investment.
We did not have cross gen accounts that held an entire gens worth of crap back in the day. Hell, Nintendo still does not have it and I think that is why you don't get the value in it.
Microsoft and Sony tried that last gen (you may have mentioned this but I wanted to reply so fast, I just skimmed it!). Both MS and Sony had a ton of cross gen purchases that carried over as well as Achievements. Hell, there are movies I had purchased on PS3 that I deleted and couldn't redownload (It's insane. I even made a thread about it.) but those purchases came back on PS4!!
Anyway, I agree with you. You kinda have to stick with the brand you've been with before or just kiss a lot of your content and saves goodbye. As a gamer, even if there's a game I never intend to play again, it just feels good having my old saves and dlc there. Switching brands is hard!!