@south_korea_ln made a great list (in a reply) and I thought it deserved its own post.

Here are a few of the main reasons:

• convenience, just need to scan a LN invoice to accelerate your transaction to the front of the mempool.
• you can use it if your wallet does not support RBF.
• you can use it for some multisigs where RBF is not available

Original post here.