It's not just you, I hear this often, but I am always suprised people can read for so long in bed. No matter how interesting a book is, I can rarely read more than 20-30 minutes before the urge to fall asleep becomes too strong.
But I can sometimes code until like 4AM. Weird.
Reading is usually more passive than coding. I'm often never sleepy if I'm actively coding something late at night but reading a book (no matter how engaging) or watching a tv show can very easily make me sleepy. That said, everyone's brains work very differently.
This is just so weird. In general coding won't let me fall asleep but a book 100% will never let me sleep until I finish.
I also find the idea of "forcing" yourself to read rather peculiar, but we're all different people. I wonder if there's genuinely something different in how the brain reacts.