If it were guaranteed that the price of bitcoin would stay the same as it is today, would you still buy it? My guess is, the answer is no. But if its value lies in being a currency, price stability is essential. And if your answer is no, how is it then not just a Ponzi scheme? In other words, everyone is buying it on the hope of someone paying more for it in the future, not to use it as a currency.
Yes, your guess is right that nobody is buying and stocking bitcoin for long periods of time. If the bitcoin value does not increase, I make sure the bitcoin is not as famous as it is now. That means people are interested in bitcoin because of their lucrative investment value. Bitcoin will only be an online payment, if its value never goes up.