Are all installations of OS X (10.8+) Case Insensitive (by default)?
By default, HFS+ in OS X is case-insensitive. You have to specifically erase a partition and select case-sensitive for a partition to be case-sensitive.

It's not that common, but there is software which requires case-insensitive HFS+. It's more common for legacy software to require case-sensitive HFS+. Of course, software should work on both, and most newer software does. The Acrobat restriction feels like a way to avoid unreproducible bug reports from users using (awkward) case-sensitive volumes.