Why would one choose train when flight is cheaper? Delhi to Thiruvananthapuram.

First off, I don't want my lack of knowledge te be seen as some kind of attempt to spread something (which I have seen often. Instead of having a little more research or asking people, some do spread the half truth as facts).

Anyway, I was casually just exploring ixigo app. I tried large distances just for fun. The flights from Delhi to Thiruvananthapuram is cheaper (around Rs.7000) than train (around Rs.8800, 1AC). Not to mention way faster. 2AC is equal to flight.

I know trains are generally cheaper. 3AC is cheaper than flight.

But I am wondering why would someone go 1AC on train when flight is cheaper?