I've used TSA approved locks on our bike cases when traveling, just to keep the cases from coming open. They always get opened in the US, with a note inside to say the case was inspected. I bought my locks at Target, not expensive, so if they disappear, no big deal.
That being said. I will never purchase a combo lock again. They tend to get 'reset" on their own. I had to find someone to cut off a lock in Italy, not a fun thing. I use keyed locks, and keep the keys in a secure place - and I bring both sets of keys (as they usually come with at least 2) I keep one keep in a wallet, and the other in another secure place.
If you don't have anything of huge value in your checked luggage, you can skip a lock, unless you worry your suitcase might open up and spill contents somewhere along the way....