You don't understand how hard it is to gain weight when you're perpetually skinny.
You're quite right, I don't understand how that could be hard. :)
When your trying to gain weight, eating becomes a chore and it gets expensive.
I can understand the "gets expensive" part. Also, I guess if you're not actually eating things you want to eat, I could understand the "chore" part, since there's only so much health food I'd want to eat in a day. If you were really just trying to gain weight, though, you could just eat those things that you can never get enough of (whatever they are for you), and easily pack away six or eight thousand calories a day, right? You'd have to do hard labor all day, like a farmer, to burn that much off.