For the vast majority of parents, it doesn't matter. If you're worried about it, invest in a baby scale and weigh regularly (keep in mind that babies lose weight immediately after birth, though.) Doctors can give you a chart for normal weight gain.

For a minority of parents, the child will be "failure to thrive" and for that you will need to measure intake, but the child will also be on special high calorie formula anyway. So at this point the advantage is irrelevant.

"Measuring" is a really stupid reason to deny your kid the other benefits of breast feeding. However, there are many viable reasons not to breastfeed, such as it's just not working, or the mother needs to work/have a life, or it's painful, etc.

I was going to ask the same question. Not once have a thought "my daughter is eating too much."

Politics, nutrition and parenting are all conversations I attempt to avoid, and this combines 2 of 3 topics. :/

With breast-feeding my wife wasn't worried about "too much", rather "not enough": it wasn't clear to her exactly how much our daughter was getting.

That said, it was pretty obvious that she was getting enough, it was just mildly uncomfortable not knowing how much.