It's light- You don't want to be bogged down with heavy syrups and sticky, thick sauces- mousse is the lighter option that leaves little trace.
You can satisfy your sweet tooth- If you prefer sweet to savouries, then this is the ideal choice because it's sweet but not too sickly.
It's tingly on your tongue- The bubbles running through the mousse burst on your tongue so it offers a delightful sensation on parts of the body above the waist too.
It's not too sinful- If you use calorie dense ice cream or squirty cream you might be stacking up the sins but some brands of mousse are designed for the more health conscious. You could easily burn off one pot of the stuff in a single session.
It's easy to clean up- While it's advisable to lay down an old sheet or a towel before using food in sexual play- mousse is not as messy as other edibles you may wish to experiment with.
It's an excuse to shower together afterwards- Although you can probably get most of it off with your tongue, you may wish to wash away any stubborn residue afterwards so why not hop in the shower and make sure you're thorough?
It's cheap- Compared to the fancy body paints and expensive flavoured lubes that are on the market right now- one or two pots of mousse is not going to break the bank.
It's a great disguise- If you are one of those people who's embarrassed to buy sex aids over the counter- no one will know that you don't plan to eat your mousse out the plastic pot with a spoon at the checkout.