Why do we force/cause/encourage/compel things TO happen but we don't make things to happen, we just make things happen. Where's the "to"? Why?
I don't know why we don't use a to, but it's well documented for this meaning of 'make'. See this definition:
[+ infinitive without to]
The wind is making my eyes water.
What made you change your mind?
Just seeing Woody Allen's face is enough to make me laugh.
The photograph makes me look about 80!
It wasn't always like this: here is a sentence from Psalm 23 of the King James Bible (1611):
He maketh me to lie down in green pastures