Because in a few years the popularity of bitcoin will become much higher. And if this happens, then we will see a price increase, directly proportional to the growth in demand for the Cryptocurrency.
Looking at the present growth in bitcoin we can easily assume that the future of bitcoin will be even brighter and it will be holding a higher price too and if truly happens then we would regret in future for not investing in bitcoins at the right time and this is that best time to invest in bitcoins.
You can look at the present or at the past, bitcoin is growing back then and now, there is no difference. Of course now when the price is high, everything is on higher level, more shops, more casinos, more sites that accept bitcoins, things are happening for bitcoin. And that is why bitcoin was and is good investment, because even on 2000 dollars for one bitcoin we will see more free space for bitcoin to worth even more then that, so buying and investing in bitcoins is always a good choice for people who are looking where to invest their money.