It's like a filter so you can focus on the top five or so players at a position. If not, imagine trying to pick which HB to sign. Rather than comparing the top 5 or 10 you would have to keep sorting by everything that goes into an HB.
You would sort by SPD, CTH, TRK, AGL, ELU, INJ, STA, etc. Each time it would be full of those outliers who are really good at one rating, but not good at others. So you keep trying to narrow it down to guys who are balanced across all the ratings, worthy of being your starter. All you are doing is replicating the OVR.
It's not about choosing a 92 over a 91, it's about not having your searches full of 65 OVR players who are really good at the rating you are sorting (i.e. 97 SPD), but not balanced enough to be your starting HB.
Nonetheless, the main point is that if you want to ignore OVR you can do so, but why take it out? At worst it shows you which players are worthy of further consideration, so why get rid of it?