why do people help make old cars look bad

As a frequent car show attendee, We have had people make comments about ours or friends cars.
so, I try and stop my kids from ever making a negative comment about someone else's car at the show.
You never know who's car it is, they obviously enjoy it, probably have a lot of work and or money in it. As I have grown older and hopefully wiser,
I have learned to just appreciate and get joy from other people just enjoying and using their cars.