We don't know the exact reason of halving, but it seems to be a great and simple way to introduce a way of slowing down the pace at which new coins enter the circulating supply, and making the process fully autonomous (no centralized authority is required to control the supply).
Supply can not be changed, and it helps Bitcoin is solid than smart contract altcoins with mint function to dump any new supply if developers want.
How is the 21 million bitcoin cap defined and enforced?Cycles also give people a feeling of something being completed, give motivation and things to look forward to in the new cycle. Perhaps it's because of how we're used to living. We have days as cycles of Earth's rotation around its own axis, years as rotations around the Sun, so cycles are just something we are very used to. Many look forward to halvings, anticipating an increase of BTC price afterwards, and miners can try to make the most out of the rewards before they get reduced.
Cycles come and go and more than that, make history. So far with three previous cycles, we have a history like Bitcoin will make a new all time high with a new cycle. Will this cycle be different, we will know soon next two years.
The best thing about bitcoin halving is it attracted great numbers of investors which made the price of bitcoin rise and create new ATH every time we reach this event, we are witnessing history
Halving is used like seeding for Bitcoin every four years and attract considerable new people, investors join this market with their money. They are new in this market and their money brings in is new capital flow for this market. It helps price to increase with same supply, higher demand, more capital is ready to buy up the price.