True true................
I don't know why either, although I've thought about it quickly just now. I don't think you can tell why because you don't know it when you're growing up until you have a "moment" of "Oh, WOW!" and then you realise. I can remember vividly thw time when I realised I liked big boobs when I saw Lolo Ferarri on TV when I was 14. I was mesmorised by her, I had a frantic excitement about me, like I'd found the holy grail!!!! From then on, it's been big boobs all the way. So basically I think it's in your genetic make-up for you to discover and so there cannot be reasons.
There's other conclusions I've heard such like it was due to being breast fed as a [censored] but I don't agree with that point. I think there's plenty of big boob lovers who were not breast fed as babies.
Lastly, something I can't work out as to whether this could be plausable is this: When growing up and you kinda get a fetish for something (ie, legs, bum, boobs) is it due to a shocking moment when something strikes you more than ever before to get you "hooked" to that specific part of a woman's body? I.e., you could be 12, and see a great pair of legs on the TV and go "WOW" to then be hooked on legs? My point being that we don't have any fetish mindset when born and growing up until "that moment" that makes us want to see more and more, and with boobs (my fetish) for them to get bigger and bigger!!!!! (Lolo was huge in her day and that wasn't too big for me then!) To conclude, could this mean that everyone could become a boob addict if everyone was exposed to big boobs in puberty? Probably not but you did ask for an in depth answer and they're just my thoughts about it. Generally speaking, I don't know why but I hope I've sparked your imaginaation a little bit..........
Take care and WELCOME to the BEA