To me, very big breasts are super hot because they accentuate physicality. Imagine this scenario:
a woman with giant boobs enters a room full of strangers. It´s very likely these people don´t think about her nice haircut, her mood, they don´t wonder what she does for a living. Instead, they think: "Dude, her tits are enormous!" Why? Because such breasts are rare, and human attention tends to focus on things that stand out. For the women having such breasts that can be pretty stressful, because not only do people at first sight fail to perceive them as a person, but a bodily feature. The bodily feature in question is strongly linked to intense physicality: motherhood, breastfeeding and/or sex.
Personally, I´m attracted to this focus on physicality. It offers joys of escapism and regression, I guess. To concentrate on physicality feels like a healthy counterpart to a daily routine of navigating complicated social and intellectual minefields. Of course, sexuality is also complicated, still there´s a lure of simplicity to it.
In addition to social aspects, very big tits are also a physical burden. They are heavy to carry around, make running virtually impossible while not serving a practical function. This offers pleasures for sadist observers who enjoy someone being handicapped by their body´s overabundance. When spelled out so bluntly it sounds rather nasty. But I believe humans enjoy lots of different variations of sadism, big breast fetish is just one of many of them.
Huge tits stand out, they are not perceived as being subtle, but seen as in-your-face-intense. As such, a taste for them might seem vulgar. A connoiseur of big tits may be the most attentive observer, catching slightest nuances of a mood, a situation. Her or she may even be very articulate about such nuances. But being attracted by severe enlargement of some body parts, this person still has to cope with the stigma of being a simpleton with a primitive taste. To be honest, to me, this is also hot. I guess because it offers a welcome contrast to always being a respectable, functioning part of society.
There´s also some humiliation in all of this. Confessing having vulgar sexual preferences is humiliating. Having your smart personality overshadowed by your big tits is humiliating. Such stuff can be hard to swallow, but it can also be a source of pleasure. Like forms of exhibitionism, finding joy in being ashamed.
