Do you "need" all the different sizes, from a user's perspective? No. One medium and one large pan, like a #8 and a #10, is sufficient to cook most anything you'll do in a skillet, with maybe a smaller #3 or #5 if you prefer smaller skillets when you can get away with it.
But, as shown by other posts on this thread, there are various things that the other sizes may do better than the common ones. You could still cook it in one of your main users, but you just get better results in a pan just a little larger or smaller.
And then there's some degree of personal preference as well, so YMMV.
I guess it's kinda like golf clubs - you don't need every size iron to play, but people get them anyway when they want to refine their game, to have the best size for a broader set of situations.
But, as shown by other posts on this thread, there are various things that the other sizes may do better than the common ones. You could still cook it in one of your main users, but you just get better results in a pan just a little larger or smaller.
And then there's some degree of personal preference as well, so YMMV.
I guess it's kinda like golf clubs - you don't need every size iron to play, but people get them anyway when they want to refine their game, to have the best size for a broader set of situations.