Here is one advantage of X that was notable, even today: Keeping user data out of user hands. A high end CAD application I used to do sales, service, sysadmin

Here is one advantage of X that was notable, even today: Keeping user data out of user hands. A high end CAD application I used to do sales, service, sysadmin for used X and the SUID permission bit in UNIX to accomplish keeping data out of users hands. On my bigger systems, I would run one application image, shared by a lot of users. This app, when run by a user, had the data permission and "ran as" data admin. The user has no permission. All access to the data was through the app. And the users had no access to the app or data, just a remote X session. I had tens of users interacting on big designs that way. No worries. Secondly, I could where needed, spawn a second copy of the app to run local to be served up to or even just ran directly by needy users and everything still worked fine. I just had the app run as a different user and the access barrier remained intact. But the big win was one application, one data repository, many users via X. I made a scripted login for them. They would launch it, do their thing, and that's it. All I needed was a respectable X server for whatever box they ran locally. I could admin that setup, and did, on a free JUNO dialup from all over the country. This was the 90's through early 00's.