Hand eye coordination, just as you said. Starting out, people have difficulty with the speed bags it takes a good deal of training and effort to develop the skills (through coordination) to be comfortable with the bag.

It is all about timing and that is why fighters are able to hit it with their eyes closed.

It helps you warm up & cool down. It gets you loose, and will make you more loose in the ring. It also boosts your stamina.

Keeping the hands up during a fight and ENDURANCE .

I don't know!

I know people say it works hand eye coordination but, I see fighters who can do it with their eyes closed, just by listening. So how does a speed bag help you? Anyone know any other good drills to do on it?