I think of it more like puppets for a stage performer, someone puts a lot of time into making it, it gets used for a handful of performances and then is boxed and stuffed away. Especially thinking of vtuber models as something showcasing the maker's talents, they only get a brief time of being showcased/advertised before their work is shelved. When your income is commission based and advertised by use of your product, you'd want it to have as long a shelf life as possible. Yeah, they get paid for their work but how many new customers would they get from someone with mouse's audience/reach using it for a year? How much money would they theoretically be missing out on?