Originally Posted by DeadHead

A loss of nose wheel steering, due to a Hydraulic problem, would definitely do it.
I think that's what you meant.

Nosewheel steering is an MEL item, but having it fail on a taxi due to unknown causes, even with a remote chance it's related to hydraulics, is discretionary to the captain.
Good judgement would be to error on the side of caution though and get towed in, but every situation is different.