Most Helpful Guy
Well bigger boobs for a lot of girls are never in proportion with their body.
Plus a lot of "curvy girls" are just fat girls who are in denial. I've had fat girls email online wanting to meet and they'd even mention their boob size (weird but they would) and their photo would just make me think she has long saggy boobs that are gross. Fat girls have bigger boobs because boobs but it doesn't mean they are attractive. So guys are typically going to be more interested in healthier girls.
Boobs aren't everything. Guys mostly like girls who are proportional. Tiny girls have cuteness factors that guys love even if they "don't have boobs."