This was common when I lived in the UK. It was considered normal and polite, self-deprecating and humble. You'd come off kind of charming by extension. Since living in the States it's a different story. I think it's perceived as odd and insecure, as others have said.
I kind of admire the confidence people have in themselves here on the whole, but I also think it can be a little over the top. It's often to the point of narcissism and bad manners towards others, which I'm not okay with.
I'm not sure where you live but it might just be part of a cultural deconditioning you'll have to undertake for yourself. It certainly doesn't gel with this bravado culture we have now.