Why?

So, I would like to tell a story of a past experience, from 1.3 - 1.4 versions of minecraft.

I spawned usual, cutting down trees doing what you would do when you first started. Then I started fitting into a first night home, you know the ones that are squares. The first night accurred and I got out a bed (only red at the time) and I slept. In the morning I started hunting for iron in a mine I made, I was a bit scared as I dug deeper since I was stupid and brought no torches. I finally reached a cave and went back up to my miniature den, when I finally made a torch I couldn't place one. I thought it was a glitch at first until I got a permanent house. Mobs would frequently spawn