I think that’s a bit irrelevant. Finance has had a culture of paying a lot and paying based on performance for quite a long time. It is also mostly easy to measure performance of a trader’s accounts or of the firm as a whole. I think some just-so arguments for this structure are that the skills are transferable and the companies are all competing with one another, so someone can easily jump ship, and performance is easy to measure so people know what value they are creating.

Two downsides of this are that it can be unfair to people who just get unlucky (eg working on a less-profitable desk), and that it encourages taking large risks for higher returns, which is especially bad if they are taking on long-term positions. One way to try to address the latter is with a partnership structure where partners are incentivised to rein in big risks, but having joint and several liability is unusual and scary.