There is simply just different agreements in place for all platforms.
So what Sony can do doesn't mean Microsoft can legally do the same and vice versa.

I think at the advent of next-gen Microsoft might make some changes to it's agreements to make the entire process easier... Then again, I thought they would have done the same after they finished up with the Xbox 360's backwards compatibility scheme.

Problem is that it doesn't matter if it's X2 or X360 BC we are talking about the agreement made at the time of the original game =p

They cant because they have to find a way to nickel and dime us off PS Now/XBL and re-release remasters at full price for us to buy. So they wont go full B/C. They know we'll re-buy the game full price, we've shown them we will hundreds of times with re-releases on ps4/xb1/switch, so they wont stop now

Still some people have proof that is definitive and certain that PS5 will have BC.

Hence why I assumed they would have modified things last gen so that things would be more amenable this gen.

Not sure what koolaid they were drinking. Sony didnt buy that Cloud service just to give us full BC compatibility out of the kindness of their hearts. Its to make us pay for it lol. Same with Microsoft. There's no reason to give us full on B/C when were all still buying what they feed us

I absolutely agree the motivator of BC is monetization, if they couldn't find a way to make it profitable there would be less or no motivation to do it. But there are some holes in your argument.

The reality is the way MS is handling it, packaging the games into new digital downloads and selling games digitally, this all requires consent of the publishers/developers or who ever owns the games. If they made a basic emulator that pretty much only runs disc, I don't think they would need permission much like the OG Xbox emulator on 360. However, their selection OG Xbox actually in the store was very small. No money is being made if people are simply using old discs.

However, it worth noting there are some games that are on BC that are only available on a disc. That means MS is actually making the effort to add games to BC they can't even monetize. Now you must admit that's actually pretty nice.

I think most people agree its probably impossible for the PS4 to handle a PS3 emulator that can run all games at full speed. So they can't really monetize PS3 games on PS4 the same way MS monetizes OG Xbox games and 360 games on Xbox One. Most people who use BC are likely using old discs and old digital purchases, but MS is still sells over 500 games previous gen games in their current store. Its not just a nice gesture from MS, its being monetized. Anecdotally I've bought numerous OG Xbox and 360 games in the Xbox store thanks to BC.

You exaggerate how many remasters we actually get. Just take into consideration most of the games on Xbox BC don't have remasters. There are many studios that would be happy to keep selling a previous gen game without having to actually port or remaster it. That's where BC comes in.

I don't think it exaggerated to say that at least on the Playstation side of things like 95% of first and third party titles worth playing on  PS3 has been made available via remasters and ports on the PS4

It's definitely a possibility with Sony since their PS4 platform pretty much allows them to extend the GPU ISA as they wish so future PS systems like we saw with the PS4 Pro may not even need to be binary equivalent or a superset of the previous systems to be backwards compatible with software built for them and for Microsoft, I don't foresee them encountering many issues either ...

Relative to the number of games released, not a significant number has been remastered. There are also a ton of games on PS Now that don't have PS4 remasters.