Convenience will always win
People just want to get stuff done. What is the simplest and least controlled way of getting a file to someone else? The email attachment. To quote Princess Leia "The more you tighten your grip, Tarkin, the more star systems will slip through your fingers." The tightening of grip often isn't done in balance with enabling productivity.
Historically there was little choice, as requesting a change to network file permissions could take weeks, but now even with cloud repositories such as SharePoint there's still a ton of stuff that just gets attached to emails, even with corporate level communications.
Generally, anything that blocks users to do something productive in a corporate environment is subject to circumvention and security risks. So, you don't have the software you need to do something simple and trivial that would take you minutes at home? Then why not bring in that unauthorised 'portable' installation version and run it from a USB stick?
Biting the hand that feeds IT
