The whole counsel of God considered, we deduce only two functions of the female breasts. They serve a sexual purpose, as in Proverbs 5:19, and a life-giving one, as celebrated in verses like Isaiah 66:11. Indeed, whenever Scripture refers to these organs literally or figuratively, the usage is exactly evenly split between the nurturing and sexual purposes.
As I argued in Proverbs 5:19 ANR biblical apologetics, one need not separate both functions. Women who are most heavily desirous of ANRs actually tend to favor the nurturing intent over the sexual, interestingly.
In the most beautiful, stable and durable ANRs, the loving, self-giving, life-enriching aspects of the nursing relationship often trump the eroticism.
Trust me readers, especially men, the best, most loving ANR partners you can find are those who desire the loving, warm, emotional, nutrient-and-life-giving facets of CN than simply getting off. Sexual release is important, but the emotional and physical nourishment is slightly superior.

See also A systematic theology of the female bosom, where references to breasts as life-givers outnumber those as sex organs by a 4:1 ratio.