There's a limit of 21M bitcoins that we could mine until its impossible to acquire, this is one reason why bitcoin's value is increasing due to mining difficulty and the scarcity of the coin in the future. The law of supply and demand plays a vital role when it comes to increasing price of bitcoin that is why bitcoin is one of the best store of value just like gold.
Silver was $80/ounce in 1980. That is like $3000/ounce today. But now Silver is $17/ounce.
All the signs that Bitcoin is going the Silver way.
Normally, we cannot expect something of value to actually remain stagnant since it is not controlled and the idea being fresh then made it as low as possible. Bitcoin actually started with no value anyway compared to silver, or I would rather say we start placing the value on them and as people keep perceiving it and keep seeing a huge demand for it, and the need to use it, that would keep causing the value to increase. Some just ended up seeing the future earlier than some of us and decided to invest when it was worth nothing.
Demand and adoption increased. That was what happened. The thing is just very few people believed in bitcoin back then and it started without any value and gradually we started placing value on it based on its usage and that is where it all started.
As people gradually seeing more value, you would not expect me to buy something for 0.1$ and give it up for the same value since I know how useful it would be, so as it keeps going, on and on, and the demand kept increasing, the price kept on increasing as well and I believe we have not even seen anything yet.