Like those that start their hodling from the year 2013 till now when bitcoin price was still low, during that time they may have stash alot of good quantity of bitcoin, so those set of people can decide to take some profit from their investment without selling all their investment, because they know clearly that they won't have that same privileged to accumulate bitcoin in such low price again. And aslong bitcoin keep growing (which it would) their Bitcoin value in their portfolio would keep increasing massively.
You don't have to be in bitcoin for more than 10 years to be able to reach a conclusion that you are able to shave off some profits without any expectation of buying back.
If you have reached a conclusion that you have enough BTC, then you could shave off some BTC at various points in time as the BTC price is going up and you can figure that you would have fewer and fewer BTC if the BTC price were to keep going up.. but part of the BIG question would be determining that you largely have enough (or more than enough) BTC in order to start to employ such a raking strategy, which I outline in
this post.