To me, you wear it to proclaim your faith. You wear it because you are a believing Christian and are proud of it, not for hope or for protection, but to show your love for God with it. To show your faith, just like someone would wear a star of David to proclaim their belief in Judaism, I would find it odd if someone was wearing a cross for 'hope" or just for fun, to me, if I see someoen wearing a cross, I believe they are Christian.
Oh, and Catholics usually wear crucifixes, not usually plain crosses, though of course, they can wear either.l