OkOk no problem but I don't understand what you mean by 'so many sync settings' perhaps if I did I could answer your question more fully.
On my Nikon I go into the Custom Setting Menu>Bracketing/Flash>Flash Sync Speed and I have the following choices:
1/250 s (Auto FP) (This is HSS)
1/250 s (Max Sync Speed)
1/200 s
1/160 s
1/125 s
1/100 s
1/80 s
1/60 s
So why would I choose anything but either the top one if I want HSS or the second my max sync speed
I think Andy hit the nail on the head when he said
So I am now assuming that they are just old sync speeds from earlier days left in for compatibility reasonsAccording to Thom Hogan, the reason for a slower sync setting is to improve compatibility as some external flash units might have a slower maximum speed. The other scenario is when working with 2 different cameras. If the sync speeds are different, then the images might look slightly different if the subject is moving. By setting a slower sync speed, shots taken from either camera should look consistent.