Why do you think one-uppers exist?

I have a friend who's child is the same age as mine.

Whenever I say anything about my son, literally anything, she will try to one-up me. For example, I got excited my son learned to clap. Her response was "Lucas has been doing that for about a month now." I also said my son finally slept 5 hours in a row, and she said "Lucas slept seven hours in a row." Like it's never supportive or excitement for me, she only wants to one-up me and kind of insinuate her son is "better" in some way.

Why do you think some people do this? Is it insecurity? Narcissistic personality? Do you know anyone like this? How do you respond?