Why? Just why?

Why do people who have had kids before feel the need to judge other parents??

To provide context: my MIL and a friend, on separate occasions after I mentioned that my son was acting fussy coz he was likely going through a leap or spurt, told me they are "so glad they never read anything" like research.

The way they both said it implied that because I research stuff I am missing out on the fundamental principles of being a mother, like instinct etc.

You do you, and I'll do what ever makes me sleep better at night knowing I'm not a failure coz my baby can't be settled all of a sudden. The research gives me reassurance, so BACK OFF with your judgment!

Ps. Sleep deprived FTM here so I don't need to be told that I'm overreacting.