If you subscribe to the theory that markets allocating capital based on supply and demand is beneficial for society (even if detrimental sometimes in the short term), then traders provide the utility of contributing to the proper allocation of resources in society (which is constantly in flux).

The fact that smart people opt to go into trading (or selling advertising) rather than research is a consequence of government underpaying scientists (or the volatility is too high, or the path to quality of life at work is too low).

Either way, if the situation is that society needs more scientists or doctors or whatever, then the government should be paying more to incentivize those choices.

Expand the number of medical schools, the number of residency positions, etc. Reduce tuition or pay graduates and residents more. Reduce unnecessary learning requirements so that one can expect to have a life and become a surgeon. Reform tort law.

None of these are under the purview of trading firms or the people that work there.