Each day, many untold thousand watts of electricity are committed towards bitcoin mining. People mine bitcoin because they hope to earn bitcoin, which has value and can be bought and sold in various markets.
Without going into too much detail, mining is the process by which the network is secured and transactions are processed. In order to encourage people to mine bitcoin (or other cryptocurrencies that also use proof of work mining), each block contains a reward.
That reward is released to the miner that successfully solves the block.
This reward needs to be high enough so as to be a strong incentive. But the reward also cannot be too much. A large reward would cause an oversupply and lower the value of the currency. blockonomi.com