Who complains about this? Gay men who are afraid of seeing breasts?
No, normal men who don't want to be accused of "staring", of being a "lecher". Parents of young children who don't want to have to get into "that discussion" until the kids are older and not in a public restaurant.
Yes, breast feeding is "perfectly natural" and a good thing. However, in our culture, the breast is continually promoted as an "eye magnet" for men, a primary fashion accessory, a means for some women to "tease" men. The fact that we men are simple minded and genetically wired to notice does not make it easy for us to remain polite and avoid staring.
Just as a gentleman will not stare, a lady will use a cloth to cover the actual transfer of that wonderful, life sustaining, "organic" nutrient.
Just avoid the "Free Range" aspect of the process.
Dude, I don’t want to see that fattie’s boobs while I’m trying to eat.
The complaint isn’t about breast feeding, it’s about her insisting she can do it without covering up, Covering up is very appropriate and done by women of any class or intelligence in our society.