Because until now bitcoin still have a great future. Because there still so many peoples believed in bitcoin and there still so many peoples invest in bitcoin that's why peoples are still buying bitcoin.
In my own points of view. People are still buying Bitcoin simply because that bitcoin is the must old and stable coin in the market. It's true that price is not stable all the time but never heard bitcoin is dying. The coin is in of the top coin in crypto. Bitcoin for me is whorth to invest. Patients will be paid by profits in the future.