Earlier quoted context omitted.
Flash bundles things like Chrome, Mcafee etc. That's the real reason they don't want a auto-update. Google pays them a lot for bundling Chrome(I think it's around $1 per install). They keep breaking the auto-update on purpose so that they can make a ton of money by bundling other software. Same with Java updates.
And that's downright weird, given that Chrome use a different plugin API and thus get Flash bundled. Even Windows has Flash via the updater. Just about the only browser that use the old API is Firefox.
Really, at this point I think Mozilla is more interested in just getting rid of plugins than trying to implement an alternative to NPAPI - why put all the effort in to support something like PPAPI when plugins should be dead within the decade anyway?