I noticed that the price of Bitcoin change much like all altcoins.
But the price of other traditional currencies like the euro, for example, are stable and do not change much.
It is the government that control their prices?
Stability is useful, but not nearly as useful as significant upward volatility. Volatility is a measure of instability, both upward and downward.
In any case, Bitcoin price cannot stay stable for long. It's a cork floating in an ocean of fiat currencies. With luck, the cork will absorb the fiat currencies' desirability.
If this happens, Bitcoin will appear stable and the other currencies will fluctuate around it.