Oh, good fucking lord, as if
The Sims 4 wasn't enough of a blatant cash grab already, they now have to license a popular franchise just to bait people into playing it? Talk about fucking desperate.
The simple answer is that it's likely a performance issue. You're going to be seeing hands a lot more than you are feet, so it's better to have the hands animated while the feet can be one solid immobile mass that conserves polygons. No sense animating something that's only visible 5% of your Sims' lifetime.