They also allow you to develop strength in weak areas. However, on a regular basis I watch lifters take away the advantage of the blocks by pulling out of the weak position they are supposed to be working and moving to a comprised position because it feels stronger to them. It is important to maintain good position even when starting in a good position in order to gain the greatest amount of benefit from block work. Here is a video of Chance working blocks this morning. Take a look at this to really see what he is missing out on from the blocks.
Chance Snatch BK Analysis