Back when the community was new, Vocaloid had just gained considerable traction with Crypton's CV series. Naturally, the first thing creators did to get it recognized was to parody the most prevalent example of the time: Miku and Crypton's mix of mundane school fuku + cyber/technical aesthetic. It's kind of necessary to give people something familiar when saying 'Here's a thing that allows you to do this without piracy or going broke! Now you can make your own Vocaloid-like voice!'
Now, there's no need to cite the CV series for inspiration. There are so many unique Vocaloid that if anything, you look ignorant to the rest of the community and there's likely an unspoken stigma if you don't speak of or know about Vocaloids outside of the Big 8. It's normal progression that when a program starts to stand apart from and differentiate itself from its competitor, people start to move away from trends that used to be common. People get older, get more inspired and informed, come up with more original ideas, and they no longer feel the urge to play follow the leader or just be a copycat.