Yes, I've seen some people saying "Oh! But costumes are just a change in Mario's appearance, it doesn't change anything!" MAN, I DON'T CARE. THEY'RE AMAZING AS THEY ARE!! (Actually, the costumes let you break blocks being on small Mario's proportions.)

And in my opinion, they increased the potential of new courses, as you could play not just as Mario.

removing them in SMM2 was sutch a stupid decision ngl they were so fun to collect in SMM1