I got tired of plugging and unplugging stuff and packing and unpacking stuff everyday.
Monitors are cheap today. 17 inchers are under $200, 20 inchers at WSXGA are $230. I picked up the 1600x1200 20 incher on the cheap. The 24 inch monitor was definitely a few bucks.
I go for eye comfort these days as I spend a lot of time staring at these things and realizing that the reason that I had to wear glasses for many years was looking at CRTs and too small screens.
The minutes of time booting up and shutting down the laptop add up. 200 days a year x 10 minutes a day x 10 years = 20K minutes.