Many and much are adjectives, but their comparative more is an adverb. Why?

Many and much are adjectives, but their comparative more is an adverb. Why?

Is more an adjective, an adverb or a noun
The adjective means more, bigger, extra, superfluous
I'm still hungry - can I have some more pudding?
There is more food in the kitchen
The adverb means more, more, more often, more often, more often, more often
He is more intelligent than his brother
I like football more than swimming
You should practice more
The old man doesn't travel any more
Noun means: more, more, more number
I'm afraid I've eaten more than enough