I am a small A cup and I hate it. The only time I think it is useful to me is when I’m running or working out, a sports bra does keep things from flying around, especially since my breasts are a lot softer since baby and breastfeeding.
But it’s never comfortable. I think a big part of the problem is that bras are generally not designed for small breasts. There is so little for a bra to lift on my chest. To get an appealing shape, I need a very snug band, and I find it constraining plus it aggravates my skin.
I'm smaller than an A cup. Try Pepper bras - I got some and immediately threw out every bra I owned. They are designed for small breasts, with shallower cups.