I prefer touch ID, but definitely want both. Other than the mask situation, a few reasons come to mind.
I have multiple accounts with a bank app. I can't use Face ID for the main one because it's not easy to avoid having my face seen. With Touch ID I can choose not to touch and select a different account. There really are times that I don't want the phone to unlock or some other action to be approved; it's very hard to avoid it with Face ID.
When I plug in my phone to my car, it often won't connect till the phone briefly unlocks. I used to just reach in with my finger. Now I have to pull the phone out of its slot and lift it to my face; that's definitely a "pull over to the side of the road" kind of event.
Until the latest OS update (watch or iPhone?), Face ID wouldn't recognize me with my sunglasses on. Now, my watch jumps in to help.
Thinking back to my last phone (6s), the times when Touch ID was inconvenient were far fewer than the times now when Face ID is inconvenient. But, I do acknowledge that when both are convenient in a given situation, Face ID is the easier of the two.