Who does a "clean install" when upgrading Mac OS & NU ver.?

Moving from 7 to 8 and need to update the Mac OS.

Wondering, do you do a “clean install” of “ALL studio SW” in such cases ?

I used to (& it sucks of course) but have been told by a couple Mac gurus, that it doesn’t need to be done as Mac OS doesn’t mess with key items involved with ones DAW SW.