Every major family of antibiotics has generic versions, and that is not resulting in the needed discovery. This is probably because the vast majority of the "investment" required is in compliance with regulations that didn't exist when the currently-widely-used antibiotics were discovered.

Some antibiotics do have a good enough safety profile that such occasional speculative use would be a good tradeoff. Elderly people are also the one group least able to handle infections! Others do not.

Which antibiotics would you use?

I was thinking of things like amox-clav, cefalexin, doxycycline, and azithromycin, and screening the patients for risk factors. Oral antibiotics that are commonly used in empirical therapy (i.e., without cultivating a bacterial culture) and have low risks of dangerous side effects. I suspect that, for example, fluoroquinolones would be less likely to pass the cost/benefit test due to their more serious side effects.