@ Youtube cover songs and monetization

So I have a question and a few comments.

Are cover songs on youtube monetized at all? I am sure if there is a link to the original artists song some of that is converted into actual buys, but what about ads from google on cover song pages or money directly to the person performing the cover?

Are people who perform cover songs allowed to gain any money from that cover? If not why not?

There seems to be TONS of people who perform fantastic renditions of songs, sometimes better than the original, why not allow those covers to be sold directly, where the original song performers/writers/producers/etc got some cut of the cover song, but so did the person performing the cover. Wouldn't a split in added revenue be better than zero revenue from the cover songs that populate youtube?

wouldn't this be a net increase in total revenue and profit for the original artists and producers by allowing them to capitalize on the talent of others, while also allowing that wayward talent to benefit from the original artists writing?