I totally disagree! BC hasn't helped Microsoft sell more Xbox Ones (which lots of people believed would happen). Which reinforces my belief that BC is a NICE to have, rather than a MUST have. If you have NO interesting games then BC is a great distraction and keeps you using your console, but I'd rather Microsoft spent the money, man and brain power behind BC to create NEW IPs for the Xbox One. Also when I had the original PS3, with the PS2 chip built in, I think I played 1 of my old PS2 games. I honestly didn't miss any of the PS2 games. This tells me that gamers buy new consoles to play new games, not old games. If you want to play old games you install MAME and go all gooeyed about retro stuff. But new consoles should be for new IPs and new experiences, for the most part.
I like Sony's idea of having curated Remasters, that they know people will re-invest in. I see no point in having blanket BC because most games in any generation are totally crap! While selecting the really good ones, that have great gameplay and story and already have a wide fan base, Sony know that the small investment of updating the game will pay off with gamers buying it again, if it offers at the very least a new look. Shadow the Colossus comes to mind.
The only way Sony will have BC is if they use pretty much exactly the same HW as the PS4, in the PS5, but just beef up everything, so everything just runs, with little to no changes by the developers. Something that bumps up everything to 8k with no developer changes would be good, but it wouldn't stop me from buying a PS5 if they left that out.