If the demand of an asset remains constant and supply decreases, the price of that asset will increase. That's a very basic lesson of economics that we all read in school.
Yep, I've had enough economics to understand supply and demand, but in the case of the halving supply is
not decreasing. It's just growing at a slower rate, and there's a big difference. There's no reason I can see that bitcoin absolutely has to increase in price because of a block reward halving. I've always suspected that this is what a lot of speculators expect, and they drive up the price in sort of a self-fulfilling prophecy type thing.
What I really don't want to see is the bitcoin market going buck wild and turning into a bubble like it did in 2017. It's not healthy or sustainable when bitcoin grows in value so much that it starts sucking in investors who otherwise wouldn't be interested in bitcoin. That's what happens in every bubble, and while it might be really fun for a while, it wouldn't go on indefinitely.