Bitcoin attracts most users only because of its rapid price increase, and its stability will lead to a decrease in interest.
Yes it is the most attracted characteristic of bitcoin. And if that is not because of bitcoin's adjustable price, there will be no more new investors that are going to enter to this crypto currency but because of this characteristic, there's a lot of investors that sees a lot of opportunity for it.
There is advantage and disadvantage if bitcoin price became stable, if the price is not flactuating it can attract more merchants to use bitcoin as payment system and you can store your money in btc without worrying that it might decrease. while for investors its bad news because they cant earn from it if does happen.