I think sony just does not think there is much point. They have tried ps2 emulation on both ps3 and ps4 but I suspect that the number of people that still care about these now very old games is very small.
And I also suspect that most people that still care about ps2 and play ps2 games have physical ps2 consoles to play them on, like me, I have 5 PS2 consoles

, making the potential userbase for ps2 emulation on ps5 even smaller.
A ps2 console can be had for just ~50$ on ebay. You don't have to do emulation. Play on real hw.