The difference is that the quantity of what is being supplied is a factor with supply of oil/gold/grain/etc.

For mining it is just necessary that it happens.

The amount of work in mining is way higher than is required to prevent another party from being able to overwhelm the Blockchain. It is that high because of the subsidy of the mining reward means if Bitcoin has a high value the reward is worth a lot.

This is factored in with the halving of the reward. Either the price will increase exponentially or the mining reward will drop. Causing mining to reduce to those who can be profitable from fees. Which rewards those who can mine most efficiently, it becomes a supply and demand calculation in a market where there are relatively low barriers for competitors.