neither supply nor demand of anything are predictable and stable why should prices be?
prices need to reflect the change in supply and demand, thats why any attempt to make prices stable is nothing but a distortion of the market and the will of consumers.
its exactly because bitcoin's supply is completely predictable and not dynamic that its such a good form of money, things priced in bitcoin reflect exactly the balance between supply and demand without anyone manipulating it by increasing or decreasing the amount of money.
Stable prices allow to make plans. You can't make large long-term plans by leaning on a low quality currency, that's value is highly unpredictable. A good quality currency gives the necessary support needed for large scale projects, that are the foundation of modern economics.
In the world of bitcoin, everything would suddenly become extremely fragile against speculation. The stock market sharks would have control over every economic aspect. It would be cowboy capitalism on steroids. The only winners would be the professional speculators, who have the funds and the experience to outplay everyone else. The doctors, the engineers, the teachers and the police - everyone who earns their money by something other then speculation, would be on the losing side.
That's the thing with bitcoiners. They shout slogans of freedom and anti-oppression, but actually the only thing they want is to be in the place of the oppressors, while having even more power to oppress everyone else.