It is mostly the weight and physical space the tube requires. They use a lot of desk space and require a decent quality desk to hold them. They also use somewhat more power than LCDs but I suspect LCDs more modern look and space saving qualities drove their adoption much more than the power usage. The way their refresh rate works also seems to cause a lot less eyestrain on LCDs, particular when comparing a low quality CRT to a low quality LCD.
What I call the "square eyes" syndrome.
After you use one for ten hours, you go home with a weird tension/buzz in your head. Doesn't happen with LCDs.