Part of the Area 51 process is finding people familiar with the network model and know how other sites on our network operate. That experience is necessary in order for a new site to function properly.
Reputation on Area 51 is extremely different than on other sites. You can easily get large amounts of it by just having been the person to propose the site or ...
This has been discussed before countless times on Meta Stack Exchange:
Why isn't providing feedback mandatory on downvotes, and why are ideas suggesting such negatively received?
Encouraging people to explain downvotes
Such a policy would not be enforceable and it doesn't solve the problem.