You may way that, but it's the tendency... There'll be a lot of not really good Overseas VBs, as well as there are Japanese VBs like that (I've seen 4 or 5 Japanese UTAUloids which aren't exactly good, but still get fanart because they have creative/nice designs). Controlling quality would only make the community elitist and drive away these people, whose very own UTAUloids might not be as good, but they might learn how to use UTAU over time, and progress to a good level after a while.
The fact UTAU is a free program might attract people without money to buy professional equipment as much as richer people, so, asking for a good recording quality might be a bit elitist and biased. Voice technique/quality should be the priority, not really clearer recordings.
The fact we notice more the low-quality VBs in the overseas fandom is that there are way more people outside Japan than in Japan itself... So, people just tend to not notice low-quality Japanese UTAUloids as much (the fact that only the most popular/best quality ones get uploaded to YT helps as well).
Of course, I may be wrong, because I'm no specialist or anything... It's just my very personal opinion, so, chillax.