Because it is known to be a good source of income nowadays. The hackers do take advantage of it and that sucks! They do bad just to be rich or profitable.
Yes, I also think that is the reason. Of course, hackers will go to the big fish and bitcoin and other cryptocurrency has a huge value so it is a no brainer, Cryptocurrency having a huge value tends to attract hackers. It is an easy money for them and it is more convenient than to hack bank account where they could be tracked down.