Bitcoin price is dependent on the supply and demand, with Bitcoin having, it means that the Bitcoin incoming supply is cut by half and in trading we all know that when the supply is lessen while the demand stay the same, it will make the price go up. Thus the value or price of Bitcoin will increase.
That's not what really happens. If it were, price won't ever slump after halving as we've seen it do after each ATH. If halving decreases supply, shouldn't it continue that way? What drives Bitcoin price is sentiment. Most people believe that every halving year causes reward per block to decrease and so there's FOMO around that event. It's an expectation that increases buying pressure as people chase price up. This pressure soon dies off after halving.
Halving reduces supply.
Well, that will suffice while explaining it to a layman but in the practical reality that isn't what it's. It is the reward to block that reduces, not Bitcoin supply.