How come no girl has asked me out or said yes when I ask them?

You can really expect a relationship with girls. You just need to let it happen. If you like someone and they like you, then there you go. But things need to happen and develop.

I've known most of them for about a year and others more. Most of them choose to friend zone me and many also like to just call me big bro or bro. I stay friends with all of them and we even joke about how I asked them out but they could never tell me why they didn't go out with me.

Hmm... I think your problem is that you are setting yourself up to be friend zoned. Anyways, here is a link on how NOT to be friend zoned lol don't take it as law, though, obviously :) http://forum.bodybuilding.com/showthread.php?t=141264311&page=1

Friend-zone just comes down to one person doesn't like the other in that way. It is what it is. They might not want to tell you why because either they just don't feel that way about you and most likely never did if they're calling you bro or big bro, or they don't want to hurt your feelings. As to why no one will take you up on a date or have asked you on a date, then yeah, more info is kinda needed. But it could be your approach, how you present yourself, mmm stuff like that. Haha, I'm spamming this since he's a home state guy *yay* but there's a guy who writes really good relationship advice called dr. nerdlove you can check out.

If you need a link to not being friend zone I think you got a big problem but if I had to ask a girl out it would be Alexis lynn

Go read Dr Nerdlove. Start with http://www.doctornerdlove.com/2013/05/anatomy-lesson-escaping-friend-zone/ and just keep on going.