especially when they take double the time a normal airplane would.
If trains took double (or even 3 times) what an airplane took they would definitely be an alternative. Given the choice between a 1-2 hour flight and a 3-5 hour train ride, I virtually always choose the train. Especially since the train drops me in the centre of the city I'm going to
The problem is they often take 10+ times what the airplane takes. From where I live to Paris or Zurich is either a 2 hour direct flight from the airport 30 minutes down the road or literally 20+ hours and 5-8 transfers by train.