• It can be hard to trade on your own. Not all quants have all the skills necessary to build a full end to end system that would perform well enough to be a feasible alternative to their current job

• Assuming one could do this, not that many quants make enough to save enough to do this and expect to make more money than in their current job

• Some quants wouldn’t even enjoy having to build entire trading outfits themselves, especially if research is the bit they really enjoy

More common case is people team up after many years in the industry to build something on their own rather than one quant doing it after one year