because sony and nintendo realised having ability to have user loaded content is a vector of security vulnerbilities, so they decided the best choice to fight of exploits is not give you the feature instead of having a competent cyber security team.

for instance, neither sony nor nintendo give you an internet browser thats not hidden. Microsoft does.

the followup question is which company has the most experience developing an OS.

Sony and Nintendo care more about preventing piracy than it does giving its userbase good features.