Some subcultures are non-conformist, and are very positive toward other subcultures. This is not one of those. The dress code is something skinheads judge each other on. It also advertises to others that you are a tough, aggressive person and that you are aligned with whites, or the working class, or whatever.

If you just went around in flip-flops and cargo shorts there is no way anybody would know that you identify as a skinhead, or know they should fear you.