>>74012716Because they work for japanese companies in a largely japan-oriented hobby. It's a lot harder to find indie western music that's open to their music being covered and monetized without royalties and none of the big companies have the kind of networking or connections in north america or europe to find that kind of stuff.
Plus you'll find that independent music producers in japan are oriented around idol pop and anime-styled music because that's what's popular and that's what has a lot of useful tools readily available. In the west, independent music producers are almost exclusively DJing nightclubs with EDM and other various subgenres of heavily sampled dance electronica because that's the subculture. It's just not an environment compatible with solo singing covers from self-styled internet idols. And no self-respecting band or music label is going to let a youtube nobody cover their songs without a very expensive licensing fee, residuals and restrictive contract terms. They don't need the exposure and it isn't a gift economy the way that vocaloid music is.