Through natural growth, I got a set of 36D's. (started HRT at 21) From a genetics point of view (as this does effect breast growth), I come from a family of large breasted women, mostly all in DD and DDD region, only my mother has D's (34D), so technically I am bigger than her.
When you have bigger breasts, a good bra is important. I always wear a bra, besides when I am in my pj's.
Breast enhancement surgery, well I have never really considered it due to my natural size. Maybe when I am older, and gravity starts to kick in, i may go for surgery to firm things up a bit and then may go up a cup size to DD.