Cutting your nails is an important part of personal hygiene. Germs and all other kinds of things get stuck under there, but if you keep your nails short, they have less of a chance of making you sick. However, if you clip your nails in public and don’t clean up your clippings, you’re going to make everyone else sick.
There’s no excuse for this kind of behavior. You don’t just cut your nails and leave the clippings on the ground for someone else to sweep up. Do grown people really need to go back to elementary school and learn about common courtesy?