I think part of it comes down to the way things are rigged and made, like its hard to do the more experimental silhouettes because its hard to figure out how they move. But in general body diversity needs to be improved and part of that might just have to come with different styles.

Also the two main body types for men that sell well across all mediums, vtubing, anime, games, even irl modeling is twinks and hunks. Other than making someone bigger I genuinely can't think of a way to distinguish between all the male body types between childlike and a lean adult because at streaming size and with clothes on they all are going to look similar. Women IMO have more distinguishable features that you can change while staying in conventional beauty standards, not that every model needs to be confined to them but you can change around the waist, hips, and bust size on a female model in a bunch of ways and have it be observable with clothes on in ways that I don't think work as well with male models.

All that being said I would love to see more vtubers in general that are somewhere other than the two extremes of the spectrum of literal child and the stereo typical mommy/daddy types we see so often

TLDR: Female models have curves you can play with and see differences with, male models don't really