why is it funny and cute when marine does it, but it looks trashy and desperate when random indie whore has the same toggle?
Is that the Place, Japan effect?
If you want a serious answer, Marine doesn't make it part of her identity, really. Her model is hot and she drools constantly over every update, shotas, lolis, whatever it is, but the way she expresses herself is closer to an otaku being taken by lust and admiration rather than a whore exposing themselves to customers.
This is also true to the gooner group in NijiJP, SKB-bu (Sukebe-bu or Pervert Club): Utako, Rindou, Gundou and Ange. Their streams were really perverted and many VODs were nuked because of the topics they addressed and the way their 3D models tangled together, but it was never with the intent to lure an audience, just to freely express their tastes and sperg about media.
In a similar way we had Matsuri and Pikamee being very open about their loli doujin collection during the early years of vtubing boom, I can go on for hours with great examples.
The way "lewdtubers" do it is like the workers in Amsterdam do: they're behind a glass, showcasing their goods to make you spend. There is no sincerity there, there is a transaction, a product if you will, and this time they don't even have to put in legitimate work on it, just dangle drawn boobs and retarded simps will flock to the fantasy of touching nothing.
I'm not saying there's no good pervs or sluts in western vtubing, but they are drowned by the sea of grifters and thots ready to fish for autists who don't understand this dynamic. If you want a few good examples, we have Mello (Chungus Dongus), CeciHime (not her focus but she knows her stuff), Margo (she is the dream artist for architects), Henemimi (she is a cunt half the time though, so make of it what you will) and Takamura Takako (one of the few true otakus in the scene that still love anime, VNs and eroges).