At the past 2 halvings, the price of Bitcoin has increase dramatically. I know history does not necessarily mean the same thing will happen again, but it just makes sense that as the mining reward decreases, the price increases.
History plays a big role in the future events. Like for instance, the past halvings had a good impact in the market boosting the marketcap to reach new price high's specifically Bitcoin. Investors and traders will expect the same would happen, thus accumulating more would give them the mentality of harvesting good profit. This will become a trend everytime the BTC halving comes every 4 years as long as it will leave positive impact in the market.