Personally I've never fully comprehended the idea of dressing up overly fancy for church.
Dressing up is certainly not required, and I suspect God doesn't mind as long as you are there. That said, some folks dress as an expression of honor and respect.
As a young man I was invited to go pheasant hunting with my then fiancé's family. I asked, "Why is your grandfather putting on a tie?" She said, "He always does that - to honor the bird."
And then I think, too, about whether I would go in Levi's and New Balances if my favorite President invited me to the White House for dinner? I wouldn't do it, so I should do less at the table with the King of Kings?
Re-entering the U.S. from a trip to Japan last summer I was struck by two things: how loud Americans are and how poorly we dress in comparison to the culture we had just been immersed in. Neither was something I felt particularly proud about.
My last church was known for its high churchmanship and formal worship. We were also two blocks from a Homeless Shelter and did a lot of outreach to that community. On Sunday morning, probably 1/4 of the men were in coat and tie, 1/2 in business casual, 1/8 in jeans or shorts, and 1/8 in smelly, stained rags. Nobody seemed to mind what someone else was wearing. We all shared the pew and the common cup just fine without regard to the chap next to us.
So, yeah, I am willing to sticking out like a sore thumb. I don't have to dress in a coat and tie every Sunday, but I'm not going to dress like I would sitting around my living room or working in the yard. I do it to honor our Lord and mark the occasion as something different and special. I neither require nor expect it of anyone else, but it is my preference.