Making things free can increase demand beyond what’s reasonable (for example, there was recently someone in the press explaining how, thanks to moviepass, he would enter a cinema just to go to the restroom). Maybe old people take trains just because they can, taking capacity from paying customers that really need the train to get to work or whatever.
I've seen that. In my small town, taking the bus is free for senior citizens. So they sit there all day and socialise because they simply have nothing better to do.
As far as I can see, highly intelligent people of roughly equivalent intelligence/experience disagree profoundly over economics. So I doubt anyone truly understands economics.