Nakamoto has never clarified the reasons for the halving. Some speculate that the halving scheme was implemented to distribute coins very efficiently at the start of the network to encourage people to enter and mine new blocks. Since the value of each coin rewarded is expected to increase as the network grows, block rewards are set to halve at regular intervals. Even so, rather than using bitcoin as a medium of trade, this can lead to users keeping bitcoin as a speculative asset.