sony playstation uses their custom os on the console and the console is custom hardware with closed source technology
steam is made to work in cpus with x86 technology, ibm pc compatible if you like to call it that way
it is like install ios on a atm cashier machine
why would you want to do that?
the console is a console, not a pc to install steam, steam is for desktops and laptops
same applies for windows, it is a very bad idea, also a waste of time and resources, why would anyone want to install windows 10 on a gaming console, to have avast antivirus on the go? windows defender? microsoft edge?
it doesn't have any sense
the hardware on the console doesn't have the capabilities to do any of the things a gpu will need to do, not to mention the very little ram a vita has, the weak cpu made specially for games and no real internal storage to be used to install any of those operating systems
there are portable devices that can run other os, but those are mostly only audio players, few video players and results are not guaranteed