It depends on context .
When I'm doing sport, they are just annoying as they have to be strapped down
When I'm buying clothes , they can be a problem as women's fashion is often designed for small breasts, not big ones
When I'm BF or my children cuddle into them, I feel maternal
When they are sore , because of hormones ,again they are just annoying
In an intimate context, with the right person, they feel sexual .
Much like a penis .
I don't see it as sexual when its attached to my small child who is running around the house .
If a man has his penis out on the subway, I find it threatening .
If I was a naturist and naked with other naturists , or a Swede in a sauna I'm sure I wouldn't even notice one
If I Received a photo of one of my phone , I'd find It a bit yucky , even if it was from my partner . If it was from a causal Date, I'd be angry .
However in an intimate context, when I'm happily participating in mutual touching with someone I love, It can be sexy .