That's an unreasonable demand. You can't anticipate which computer you're going to want to check your email on, for example. Now this might be a good idea for just work-related passwords (as they only need to be used on work computers), but the problem there is that for non-web applications, you're probably going to have to copy/paste the password from Keypass.
> use an OS that already has something similar installed
I don't think I actually need to explain this. There are plenty of reasons why using a non-Windows operating system is not an option for many companies.
There's also the issue of installing Keypass itself. I see it has MSI packages available, which I know sysadmins at big companies like. There might be some other technical requirements for the password-storage software itself.