Why do we need acrobat readers after all? Why arn't some types of files made to be read straightforward?

PDF files are made so that editing them will be a bit harder to do. they will not also change even though you are using a different computer with different fonts, programs etc. i usually save my doents on PDF format so i can be sure that even if i will be using someone else's pc, my fonts, my alignment, my pics and my formatting will remain the same.