Benefits:
- Canon Robustness
- Felt on the inner side (anti-reflective)
- Ease of assembly (marks on the lens hood and lens, 1/4 turn and voila!). You can return it in storage.
- Protection against shocks to the lens
Disadvantages:
- Price: should be supplied with the lens for the price of one
- Difficult to manipulate the lens cap when mounted, but with time we take the hand
Personally I would say it is impossible to do without.