The rapid price growth of the bitcoin in this 10 years made the people to think thast it was a bubble and there is a theory says that if something had huge value in short term will explode at one point so that is the reason of bubble story.But people don't understand why the price increases rapidly because of it limited quantity.
But the reality is that it is not a bubble but real increase in the price of bitcoin, in fact the rapid increase in the price of bitcoin is only becasue of the increasing demand of bitcoin which reducecs the supply and therefore the price goes up, as time pass bitcoin is becoming more popular and which is also increasing the bitcoin demand constantly while the total amount of coin for mining is decreasing which is also a reason for increase in bitcoin price. 
So don't neglect it by saying bubble stories.