linux - Why unprivileged user can't change file ownership?

From chown(2):

Only a privileged process (Linux: one with the CAP_CHOWN capability) may change the owner of a file. The owner of a file may change the group of the file to any group of which that owner is a member. A privileged process (Linux: with CAP_CHOWN) may change the group arbitrarily.

What's the reason for this restriction? Why an unprivileged user can't change file ownership of a file it owns (ie. no /etc/shadow)?

$ touch blah
$ chown root:root blah
chown: changing ownership of `blah': Operation not permitted

Answer

By allowing users to "give away" files you run afoul of various features of the OS. Such as:

Taking up another user's disk quota.
Impersonating another user (or even root) via setuid.
Having insufficient privileges to undo a mistaken chown.
Making it appear that someone else had created a given file.
Setting up cron jobs to run on other user's accounts.
And many more...

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