Basically, they are expecting that the price will grow as they sit idly on their hands. But this growth is not possible without other people actively using bitcoin, paying with it and selling for it - all those people who help create real value of bitcoin. And I know what hodlers are going to say in reply. That they diminish the supply and thus also contribute to this growth.
Your point is valid in some way but I dont think saying parasites to the hodlers is justifiable as everyone cannot do trading (may be due to lack of knowledge of TA or time constraints or some other reasons) so they want to be part of this space (for the sake of money may be not the tech behind it and to be frank most of the people here are for money if it was not like that then we would not have been seeing bitcoin at this level).
Parasites is the right term for those looking only for financial benefits via someone else doing all the dirty work for them, whether you or anyone else likes or not.
And for the buying with bitcoin part let me tell you bitcoin is not yet globally traded as currency for everyone to use it as an alternative of fiat currency to buy the necessities.
This is not the problem. Bitcoin or any other cryptocurrency may never make it as a means of payment, and that would be the real problem. It is quite possible that it will remain a niche instrument with a limited use, like digital gold but stripped of its gold aspect. In fact, this is what happening right now with altcoins. They seem to be losing their speculative component, but without it they are mostly useless, apart from a few altcoins like ethereum, litecoin, doges, which have their own areas of application, no less limited.