Usually that isn't an issue, because nobody wants to be responsible for moving a wedding cake. But occasionally I'm glad that I have the clause in the contract.
Today was a good example. I arrived at a hotel that's recently been renovated only to have the caterer tell me that I couldn't set the cake up because they were going to have the ceremony in the same room. She asked if it was something that they could set up, and I told her not really, because I had to do some final touches on it once I put it together.
So she went to find a table that I could use to set it up on, and she'd have someone move it into the room after the ceremony.
This is where I ended up setting it up:
Luckily, I know the caterer who was there (I made her daughter's wedding cake years ago) and I know that she knows how to move a wedding cake. But this kind of situation has the potential to end up very badly.
Make sure that your contract covers any kind of situation that could commonly arise. You'll never be able to cover everything, but the cake not being moved is a biggie.
What weird clauses do you have in your contracts?