2007 Chevy Silverado Warranty vs out of pocket expense

We took our 2007 Chev Silverado to a Chevrolet Dealer for warranty work because of a steering wheel noise and the dealer replaced the steering gear box. As a result they claimed the truck now needed to be realigned due to the warranty work and we would be responsible for paying.

My question is why are we responsible for the cost of the alignment when the truck did not need one before going in but was a result of their work?

Any insight is greatly appreciated.

D. McElroy