It is a taxi owners licence. so why does a dispatch company hold those licenses when the drivers are the owners of the taxis?
Because they bought them, rather than the owners of the vehicles buying them.
Why does anyone on a progressive board that values labour at least as much as capital even try to defend this?
I don't think anyone's saying it's better this way. But I assume the City's interest is primarily in ensuring a reasonable fleet of inspected and licenced taxicabs on the streets, rather than the relationship of a driver to the means of production.
As we've pretty much all agreed, making licences non-transferable would end the leasing of plates, but as long as they're transferable, whoever buys one can sell it, rent it, buy more, etc.