The comparison to a snail also highlights the fact that man is a creature of habit. Just as a snail follows the same path day after day, so too does man often get caught up in routines and patterns of behavior. This can lead to a sense of stagnation and a lack of progress, which is why Shakespeare also compares man to an actor who plays different roles throughout his life.
The comparison to a snail is also a reminder that man is a mortal creature. Just as a snail eventually reaches the end of its journey, so too will man eventually reach the end of his life. This is a sobering thought, but it can also be a source of inspiration, as it reminds us to make the most of our time on earth and to live our lives to the fullest.