[MrForbes]

because all jobs don't have the same requirements.

In general, fine threads allow for more clamping force. Coarse threads work better for soft materials. You'll see coarse threads used for screws that thread into castings, and fine threads used for screws that thread into nuts or into stronger materials such as steel.

For some applications such as aerospace and aircraft, weight is very important so each fastener must provide the most strenght possible for the weight. In other applications ease of machining and assembly might be more important, so a coarse thread would be more economical.

On a robot, it would be nice to standardize everything so you only have a few different sizes of fasteners to deal with (for the sake of your sanity, if nothing else). I tried to get 1726 to do this with the 2007 robot, which meant I had to stop by the hardware store just about every day during build season!