Female streamers are judged primarily based on their appearance. Using a vtuber model allows them to be judged by their personality and ability to entertain instead.

There are in my opinion a few aspects to that.

There's the appeal of the actual model. If you look at the whole scene, theres a clear bias towards anime style avatars. But even in the sea of big-eyed, no-nose lookalikes with various flamboyant haircolors there will be some that will stand out to you personally. You can attribute that to taste or personal preference. This aspect can range from legitimate reasons like "I'm a professional digital artist, and the diversity of vtuber models fuels inspiration for my own art" all the way down to "hehehe, anime tiddies". I personaly like Bao, her model is clean and animated, her proportions aren't to wild and the collors and accessories are limited, it's aesthetically pleasing to look at. I never watched her streams, but if she pops up on a youtube short, i give it a watch.

Then there is the community aspect. Not so much the viewers but the streamers themselves. When I previously said that the power dynamic between men and women on the internet is reversed, that was a vast oversimplification. Women get still harrased and stalked if they show their face (they just get IN MY OPINION appropriately monetarily compensated for that risk). So if a streamer wants to hide behind an avatar they now have a community framework and an industry that supports them in the form of vtubing. This opens up more opportunities for talentet people that would otherwise be afraid of judgement to try themselves in the entertainment industry. Again you aren't supposed to enjoy every streamer, you are looking for that 1 in 10.000. If that marble rolls into a vtuber, then thats how it is. The more opportunities, the more marbles, the more likely somebody is going to be good.
But the community aspect also backfires a lot. Filian once commented on how exhausting it is because everybody expects all vtubers to be best friends with each other, whether the actually like the person or not. If somebody steps out of line theres drama, and you really don't want to piss of a community that is willing to spend 1000s of dollars on anime girls each month. Imagine if you were required by your employer to nurish intimate relationships with everyone of you coworkers. This gives the community an overall wholsome vibe, but below the surface it's kind of sad and creepy.

If there is sustained drama, it's often manufactured. But in the same sense reality TV drama is manufactured. People know what keeps viewers engaged and choose to lean into it. Everybody loves a piece of jucy gossip, and vtubers hanging out with each other off stream is a big aspect of that. A large part of the vtubing world is talking about what he said, she said, he did, she did and with whom. That's your gossip. And you even get a live reaction from the person the gossip is about because their chat is a bunch if narcs. Often times they even call each other on stream and open up with "what did you just say about me?". Its often lighthearted and in good spirit but still, you get the point. It's this generations reality TV, but instead of spraytanned jocks being menaces on the streets of New Jersey you get anime girls talking about sex stuff. Its really that simple.

OK, do you ever had an actor or actress or director for whom their name alone on a film is a must watch? Aubrey Plaza, Christoph Walz, DiCaprio, Robert Downey Jr., you get it. And I know I mentioned her a lot but Filian is also on that list for me. And I know this sound a bit red flaggish but at some point I was just intrigued and asked my self "Who the hell is this woman?" The fact that she happens to be a vtuber and not a actress, comedian or writer is just the fact that vtubing has the broadest appeal compared to most forms of entertainment. Let's plays, watchparties, just chating, reactions, music, education are all possible in the vtubing format. She for example did PO box streams, an interview with the CEO of twitch, visited an animal sanctuary, hosted multiple game shows, attended twitchcon on an iPad all within a year. Theres barely anything that the medium doesn't allow, especially when you are creative with it. It's just that I realized that consuming this kind of content for 3 hours a day is unsustainable and unhealthy.

So that is in fact what's so interesting about it, it's a creative outlet with the highest appeal and the least limitations. If it has internet a vtuber can go there and to their thing.