Then again, it’s not about Linux, it’s just about your-favorite-few-click-program not being available for Linux.
There’s nothing technically preventing Adobe from making Reader & Acrobat for Linux (they actually used to, around 2007 I even worked in a L10N company and we tested it.) It’s just a business decision.
Once you start asking questions of why eg. Photoshop is not on Linux while eg. Firefox, VLC or GIMP are on all platforms, you will learn stuff about the world, which has little to do with Linux per se.