It's because they told themselves Bitcoin will continue to rally forever, mostly on what they've read on boards like these. That's the only reason they can stay content with themselves - and the same reason why they'll likely lose everything in the end. Holding is a two-sided sword: it protects people from panic selling, yet it also obstructs profit taking and cutting losses. It is absolutely no 'safe route' as you describe it: it's a route that requires one to shut his/her eyes and ears, and not act on any external stimuli that runs counter to ones own observation.
I do laugh at them a little, but feel sorry for them at the same time. It's mostly the people that have no idea what they're doing in my opinion that settle down to become a 'hodler', because it feels safe.
As I write this, there will be hordes of them thinking at this very moment: 'Yeah, but Bitcoin went back up after late 2013/2014, so it must happen again!'. There is no such guarantee, and if Bitcoin gets overtaken by new technology - something which appears to be already happening (given how much Bitcoin's market share dropped in a mere few months!), they will very likely end up holding the bag. Those people deserve to hear this perspective as well, so that they again start weighing their options and do the right thing.
What about holders who really are just diversifying their assets portfolios? Those who actually seriously understand the risk, but are just putting their eggs in several baskets? No need to feel sorry for them (or laugh at them).
I do feel a tinge of disdain for the Bill Gates and Richard Bransons who have so much money and don't really know or care about Bitcoin and are just "investing" in its future by buying several million worth. Probably chump change to them.
Those blokes are obviously more careful, and not putting all their eggs in one basket. There's indeed no need to feel sorry for them, but I wonder how many true Bitcoin holders have actually diversified - especially with regard to the smaller consumer-level holder that doesn't got much to spread.
They are apparantly seen as people that have taken 'profit', while profit can only be measured in fiat currency here. Without selling, they won't have profited at all. If you bought at 500, am still holding now, and the price goes down to sub 500's (let's just assume it for a moment) you will be at a virtual loss. Once it becomes clear the price does no longer recover above this level (for example when Bitcoin gets overtaken by some alternative), this virtual loss will become a real loss.
This is the fate that many hodlers are threatened with, and many will not sell until after they've lost most they put in - despite the possibility to make monster gains.
They will have willingly skipped the possibility to take profit, because they got the impression it was a safe strategy by reading whatever gets uttered here.