Back in the day, one Soviet woman saw another standing in a long line, snaked across two blocks. "Come, I saved you a spot," said the second. "What's in the store?" asked the first. "I don't know, but everybody seems to want it, so it must be worth the wait," responded the woman in line.
For the same reason have speculators purchased cryptocurrency. Bitcoin became desirable because people wished to buy it, and even more desirable when its price soared. The popular basis for owning cryptocurrency has been, quite simply, because today's quotes will be higher tomorrow.