Then why we haven't cured cancer yet or malaria or global warming or psychological disorders ? There are a lot of smart people in the world but we really can't afford to work on silly things.
In fact it wouldn't surprise me if some sophisticated neural net algorithm developed for HFT was repurposed and used successfully for other things - medical research, climate modelling, brain research - basically anything involving non-linear dynamic systems.
Only problem of course is that all those HFT algorithms aren't FOSS, but the incentive to develop them in the first place would be greatly diminished since they'd lose whatever edge they had almost immediately after publishing.
The markets are a pretty decent lab for experimentation and learning about complex systems, which we're still not so great with, as long as systemic risk can be prevented and every player forced to take their losses instead of passing them off to governments. I personally don't think HFT is remotely as much a problem as what caused the financial crisis - a few flash crashes here and there plus an "HFT tax" on asset prices, vs the arguably-fraudulent origination and dissemination of trillions of dollars of bad debt resulting in the near total annihilation of the global economy. I think we'll gain a lot more (or at least lose a lot less) as a society by prioritizing the latter problem.
Well, smart people's labor isn't your property to allocate. Nor is it the property of "us." It belongs to those individuals.
So it's not a question of what "we" can or cannot afford.