It seems to me that if you have a person or persons in possession of a commodity and by using that commodity in a certain way, while expending just a very small fraction of their holdings they could potentially increase the market value of the commodity they are holding or perhaps just stem/slow the decline of its market value, that would seem to be something worthwhile to engage in, provided doing so did not require a large amount of time or resources that could be better spent.
In the case of bitcoin, creating a lot of dummy transactions to create an illusion of economic vitality in the interest of increasing the value of your stake in the economy requires little time, effort, or resources beyond the initial creation of a small program or two, and thus places it high on the list of explanations for what is going on here.