If the price goes back down again to around $4000-6000, people will be able to buy whole bitcoin, I know people can buy fraction of bitcoin, but buying whole is a better deal.
You DO know that it is not necessary for an investor to own a whole number of any cryptos? (Save for NEO I guess, which functions more like a "Share" of the NEO network).
Holding 0.1234 or even 0.012353 BTC or whatever fraction of 1 BTC is perfectly normal and fine.
Also, the rock-bottom level of a massive crash have been increasing progressively. The next time it crashes, it will very likely yet again be higher than the one that occurred this time on the 6th of Feb 2018.