The two main issues I have with them are that firms tend to give them to just about everybody (instead of just to folks working very directly with real IP), and they only pay base salary, not something closer to actual total compensation (often multiples of the base pay).
Having said that, the quant firm is relatively unimportant and not a good reason to prevent a total noncompete law. It's probably better to just ban them then try and make allowances that aren't full of loopholes.
Welcome to Crony Capitalism (which should not be confused with traditional capitalism).
And if the market colludes to handcuff vendors (to the benefit of the hiring companies) how is that being competitive?
Employment is already at will, and that is mutual to both parties. Why should one side be allowed to purposely disadvantage the other side? How is that being competitive?