The "Minecart Rolls" subtitle only shows up when a minecart is placed, but not when the minecart is actually moving.

How to reproduce:
1: Turn on subtitles
2: Place down a minecart on rails. You can see that the "Minecart Rolls" subtitle appears.
3: Move the minecart around. (A circle of rails and powered rails works best) You can see that the "Minecart Rolls" subtitle doesn't appear in the subtitles.

This doesn't really make that big of an impact on the game, it's just something that I noticed when I was working with minecarts.