The extent to which "it matters" is subjective, I guess. I'm now the parent of a 2-year-old toddler and we didn't track any of that, we just were on the look for obvious signs of alarm but if everything looked normal we didn't count any of those variables. Everything went fine.
In fact, we almost had a problem due to "too much data tracking": in the first weeks, there was a point in which the baby hadn't gained weight for a week so the pediatrician suggested to give up exclusive breastfeeding and give him some formula to complement it. After some thought, we decided against it: we were quite aware of the benefits of exclusive breastfeeding, saw that the baby was otherwise looking and behaving fine, thought that the data on such short term maybe would not be significant, and gave him another week without changing anything. Next week, the baby was growing just fine, and he was exclusively breastfed until 6 months.
That said, if there's something I have learned as a parent is not to judge other parents, because no one knows what the right style of parenting is (and even when we know that option X is better than option Y, real life often makes it impossible to implement). So if data tracking apps work for some parents, more power to them, of course.