Sony's legacy is an odd one. On one hand they were big in PS1 BC in first edition PS2s, and PS2 BC in first edition PS3s, so it looks like when it comes to promoting BC hyping the launch they are all for it. But then they drop it fast.
Sony actually had near 100% compatibility for PS1 games on
all versions of the PS2 and PS3. They also had near 100% PS2 compatibility on the early PS3 models, before reducing it to about 70% compatibility in a later revision, and then removing it altogether soon after that.
With their portables, they had developed a very good PS1 emulator for PSP to play downloadable PS1 games. They then carried this over to PS Vita and PSTV, which also had excellent compatibility for downloadable PSP games (barring some strange licensing restrictions).
When PS4 came out in 2013, they started off with no backward compatibility...but they did promote cross-buy games with PS3 and/or Vita versions of the games. This was an excellent way to start off with an "instant library", during a time when Microsoft's Xbox One had
no backward compatibility whatsoever.
Then, about 2 years later, there was a role reversal between Sony and Microsoft.
Early PS4 owners all assumed that compatibility with the PS1 and PS2 games would get patched in later. PS1 never happened, and PS2 only came in the form of about 50 downloadable games, which were
not cross-buy with the same downloads on PS3.
We've now seen how both of these companies have had their ups and downs in their attitudes toward backward compatibility and cross-buy. As consumers, we should want
all of these companies to learn from the past, and to adopt best practices going forward.
Sony rakes in truckloads of cash from PS Store and PS Plus subscriptions. There was just a thread here yesterday boasting about this. There's no reason they can't invest a small pittance into maintaining the online stores for their older systems, considering that their competitors are doing the same.