Snipping tool doesn't exist on hospital PCs?
Also, GPOs can (and do) disable the Windows Store. So moving MSPaint to the Windows Store does not make as available as having it pre-installed.
Still, there are times when you have a weird error you need to screenshot, and you know that if you move the mouse or hit anything other than the print screen button, it will go away.
Paint made this scenario very easy to deal with.