It might not be needed, but it's about the approach. You don't need all the tools all the time, but knowing what patterns are available and having a good understanding of why you would or wouldn't use it means you approach a problem starting from a different place.

It's possible to get the same end result most of the time (especially if the end result doesn't require the "clever" solution), but I would also agree that there definitely is a difference in approach that is discernable by watching someone work.