If a player stacks a lot of boats around a villager it is possible to trap a vex in a boat.   The vex will sit inside the boat not doing anything until they despawn.

This can be used to create "raid farms"   which have a single villager surrounded by boats at a pillager outpost location.    All pillagers will pathfind to the villager and they can be killed via lava / falling etc.  The same may hold true for minecarts however I have not tested this theory.     If vex's did not get stuck in boats they could still kill such villagers in these farms and they would cease to work.    If no mobs could get put into boats (that were not in water) it would probably fix a lot of mob farming issues.