People buy a computer when the utility they will derive from it outweighs the monetary cost. They know they may get a better deal in the future, but immediate needs may outweigh potential future savings.
Bitcoin is being criticized for having built in deflation (not incidental deflation), thus comparing it to a category of goods (computers) that is also exposed to almost algorithmic deflation is relevant.
So, given the built in deflation of Bitcoins, if you have some Bitcoins and need or want product X, why is knowing that you can have two X in a year, or four X in two, if you just hold on to your coins, going to keep you from getting your X now?
Isn't that too, as you state, a question of whether "the utility they will derive from it outweighs the monetary cost" ?
People buy a computer when the utility they will derive from it outweighs the monetary cost. They know they may get a better deal in the future, but immediate needs may outweigh potential future savings.