Why can't jQuery support object prototype extensions?

Why can't jQuery support object prototype extensions?


Of the 4 total bugs found when searching for hasOwnProperty, each one
reports that jQuery doesn't support object prototype extensions
because of some factor. In the most recent case a bug was closed
invalid with the following explanation:
"jQuery does not support changes to Object.prototype. The additional
Object properties become visible to for-in loops and breaks any code
that uses them. "
After going through and editing the 30 or so references to unsafe
for..in loops I was able to compile my application which extensively
uses custom functions on the object prototype. I guess I'm confused
as to why this cannot (or will not) be integrated into the jquery
code.
I'll admit I'm not a jQuery expert, but I couldn't find any code using
inherited objects in the for..in iterations. Maybe it has something
to do with jquery pluggins.
Of course my solution is to modify the codebase every time a new
version is released, but this seems pointless if making the iterations
safe would resolve the problem altogether.
Just curious, any info welcome.
Thanks,
Marcus