They did it to modernize it. There have have been like 50 Batman costumes and 20 different Iron Man designs in the past 20 years. Let Spidey get something new and not so hokey looking.
Making people look like hobos is the way of modernizing?
But, in all seriousness, the costume looks like shit. I don't care if it was to modernize it or not, the one from 2002 looked better.