It is not 3% each day but there is a very consistent growth for Bitcoin right now. This is mostly brought by the upcoming fork which is deemed very important for Bitcoin holders. For the past instances of Bitcoin Cash and Bitcoin Gold, there are free of these two kinds of coins to the Bitcoin holders. That is why, right now that B2X is coming, people are rushing to shift to Bitcoin in order for them to avail of the free B2X coins. The demand therefore rises.