Dear, there are many reasons behind buying or investing only in bitcoin is that it is only the strongest digital currency out there. If we talk about the current scenario Bull run is on the way and is halving is too near where bitcoin can make some price correction which will give buying opportunity to the investors it is saying that bitcoin will reach 170000$ in this bull run because there is many positive news in current time which bullish to investors to buy aggresively. DYOR it has less risk as compared to other altcoins.