Why are breasts sexual objects?

Biology and social conditioning.

The breasts and buttocks of a woman convey certain things. In humans, they're constantly doing this, in other primates it's only temporary -- when they're ready to mate (buttocks), or when they're looking for a more nurturing partner (breasts), these body parts would become larger to signal a female's willingness and desire. It is theorized that while all males are attracted to the enlarged buttocks of the female (something that is permanent in humans), females prefer to mate with the more dominant male to ensure strong offspring. Once she was pregnant, her breasts would enlarge and the dominant male would leave, his job done. At this point, her main concern switches from sex to safety, which is where the other males come in -- they compete for her affections by proving how well they can provide for and protect her. Whichever male provides for her the most 'wins', and sticks around for the next few years. He gets sex, she gets safety. Just as women have the drive to bear children, men have the drive to spread their seed, whether we're seen as a dominant male or not.

While society has changed, our baser instincts have stayed the same. When asked which type of man a woman wants to have a one-night-stand with, they pick the more masculine. When asked which type of man a woman wants to have a LTR or child with, women tend to pick men who are more average. Men who can have great success with women when it comes to sex know it, and aren't as likely to settle down. Another example is sperm banks -- most will not accept sperm from men who are under 6 feet tall, because women almost unanimously pick the traits stereotypically reserved for 'real men' when picking the type of child they want.

That is the biology of it, why we find certain things attractive. Privacy and breast fetishism is purely societal, thanks largely to religion. If religion did not tell us that certain body parts were 'evil' in public, and society did not dictate that people even in hot climates had to be clothed when not on the beach, nudity would not the be issue it is today. Nudity would, of course, portray a readiness to have sex and bear children, but there wouldn't be as many old men thinking about groping you as you'd think. xD

Simply put, they haven't been made sexual, they have always been sexual. It is sex itself that has been changed. It has ritualized, subject to rules and expectations. Rather than focusing on the biological imperative we focus on the orgasm.

On another note - Concepts such as morality, monogamy, civilized behavior, virtue, fairness, and family have all but replaced the practice of breeding with the strongest you can find. The downside to this is that genetic flaws that would previously be weeded out are not widespread, and we're suffering because of it. When the near-sighted, overweight computer tech has a child with the asthmatic, diabetic secretary with an inherited calcium deficiency -- well, it's not pretty.

Breast represent comfort, nutrition, and safety. To me their not that big a deal, but I like playing with them and my girlfriend loves being the object of so much attention.

hmmm...
I'm guessing because you can see them without actually really doing anything. Women like to show them off, and their an everyday object, but somehow society has taught us that they are sexual objects.
I don't get the fantasy's that men have about lactating women, or anything like that. Most men are breast fed, so why are they so turned on by them?
Personally I don't see a butt as a sexual object. I mean I imagine me just grabbing a girls butt and pulling her close, but not much more than that.
I think the butt, and breasts are something to grab hold of during sex. Some people call them' fun bags'.
I'm not sure I I'm being too forward, or too bold saying all of this. I'm sure I don't represent all men as a whole.
In short I'm not really sure why breasts are such a sexual object. I mean in teh womb both male, and female start out with breasts. It's not until our sex is decided that we either form breasts or not. This is why males have nipples.

It has always been like that, men look for breasts in women as a mating instinct probably to show that she can nurture the child.

It's something of an american phenomenon. In europe, breasts are subject to much less fuss.

They're considered "private parts" ... they're always covered up and such..so when people see them.. they get recognized in different ways.
I don't get public breast feeding...why can't it be done in the home? A woman pulling out her breast in a restaurant is just a WTF kind of thing.
Also, I don't understand why butts are sexual objects either...it gets the dirty business done and that's it, lol.

it's as simple as we like to do/see things that are usually unacceptable.
women don't walk around topless, hence their breasts are always covered and this is what make them so appealing to men.