why are darts in clothing so high?

I am now getting small enough to wear more fitted clothing, but cannot wear any shirts with darts, because the darts are always too high. I know it is really that the "girls" are just too low!! This is so frustrating! I have tried push-up bras, support bras, etc., and still the "girls" are too low. I guess I just have to keep looking for only shirts without side darts It is very hard to find nicer fitting shirts without side darts! SueZ

Thanks for responding, Kate! I was able to find some helpful information out about this. A lot of my problem was probably not getting the correct size of a bra. Even with my bra change, I still have a terrible hanging problem with my breasts and have trouble with the darts not lining up. This makes the shirt look way too small. I never used to wear shirts with darts either, but that is all I can find in the less expensive stores (WalMart, Sears, etc) for the button-down short-sleeve shirts. Oh well, I guess I will stick to cotton T-shirts for awhile longer...