Technically, everything any human ever does fills some kind of need, psychological, biological, or otherwise. We speak because we want to express ourselves. We eat because we're hungry. We have sex either to procreate or for physical pleasure.

So, if you look at it in a technical sense, then everything we do is motivated by some kind of need.

However, many things can also be looked at in a philosophical, "I think therefore I am" sort of sense and realize that sometimes desperation breeds greed and boredom breeds necessity.

Furthermore, you could look at things in a religious perspective and figure that you are hungry because you have not had your loaves and fishes, and you want sex to further the species as long as you're married, and you have been given the gift of writing by god.

So, yes, we are motivated by necessity or desire or even psychology or religion or whatever. That's what makes us work, our motivation. However, not every want is selfish and not every need is psychological.

I love debating psychology.