One of the reasons domain prices are low is that people register domains they are not using.
Just like they buy books they don't read. Or buy jewelry they don't wear. (And yes bring on all the replies about the differences that you want but keep in mind the time you picked up the last item on the shelf at the drug store that maybe someone else had a greater need for down the road. Or took the last seat on an airplane.)
No problem with buying domains and letting them sit there until you decide what to do. No problem buying domains that you think you could sell either, in general. As much as this might piss people off who feel the domain should just be there ready when they want it.
Squatting would be registering a domain that specifically (edit: and reasonably) belongs to someone else. Say you hear the local pizzeria opening is called "xyz pizza" and you register "xyzpizza.com". Despite what the media and all the typical articles say about this.
By the way when you say "all registered for various purposes" there is no qualification about what the purpose is so essentially some people would define you as a squatter depending upon the way they see this issue.