Why? Simple: because commercial sw want them, they need something they can made at home without giving ANYTHING to the community, ESPECIALLY if the software is crap, as 99% of commercial sw are, to avoid being depicted for what they are: vendor of crapware.
Why all such systems state they add security while they do the contrary? Because they demand to the upstream handling all deps, witch means that a generic student who have write a simple chat client need to take care of new releases of SSL who he/she do not even know much because that's just a deps of some wrapper he/she use. They state "but they are isolated", true, but they need to punch holes here and there because your snappyfied firefox need to download files, let's say pdfs, your external reader can read and so on.
That's just playing the Windows game not knowing it and refusing to know what a modern FLOSS system should be, like Guix or Nix.
Unfortunately most FLOSS devs see commercial software and try to mimic it without understanding that ideas behind it might be also technical but in general they are economical, and to support a business model they accept technical crap. Much FLOSS devs fails to understand that FLOSS model is superior IF done the FLOSS way, inferior if it try to mimic some other models not knowing why.
If only people knew the past, the classic desktop OS with the OS as a single application where anything is just a bit of added code in the hand also of the end users, no commercial software today would be able to compete. But most do not even know the past, do not even know that some modern tech was invented in the past in better ways than today and do not understand that the Conway's law is more generic than it appear, goes beyond Lisp and have a generally valid meaning in paradigmatic terms.