The "prestige," as you call it, is necessary to get a job in academia. Where you publish your research is considered a trustworthy approximation to the quality of your research, and requires a lot less time & expertise to vet.
Basically, the same reason why it's easier to get a job offer if you already have a job at a great company: "Someone vetted him for us, he is probably good" - so much easier for those hiring this way than if they'd actually had to check your previous work.