I don't really think people had practiced dca during 2013. Even a lot of people didn't have the idea that Bitcoin would continue going up to what it is today. A lot of investors or holders from 2013 sold more of their Bitcoin and had less, only a few were lucky enough to have a good amount of Bitcoin in their wallet till today. However, dca does not require much evaluation and analysis. It is easy to plan, a certain percentage should be removed for dca while the rest go in for upkeep and emergency funds.
I agree with you: you usually do DCA on some asset that you want to keep acquiring because you strongly believe it will keep growing in value in the future. Bitcoin back in 2013 was still very risky and pretty much a huge bet, doing DCA on such thing would be very unusual. For sure someone did it but we're really talking about very few people.