Diamonds don't always spawn in chests in NPC villages so it's not unfair at all. There are a whole host of items that can appear in those chests, ranging from leather to diamonds, and even iron tools. If you think it's unfair, don't steal them from the villagers, you thief!
"Sorry, I stole all of your stuff, but it's okay; I've got loads of wheat to trade with you! Oh yeah, it's your wheat by the way... Sorry, I'm a kleptomaniac..."
I'll make a diamond sword, maybe the blacksmith wants it back?
"Sorry, I stole all of your stuff, but it's okay; I've got loads of wheat to trade with you! Oh yeah, it's your wheat by the way... Sorry, I'm a kleptomaniac..."
That's what I though when I had 2 diamonds without earning them.
I'll make it up to them in trading.
I'll make a diamond sword, maybe the blacksmith wants it back?
And where did they come to acquire 2 diamonds?