Let's distinguish two kinds of motivating states. On the one hand are non-representational drives, such as lust or hunger. They're pure 'affect'/emotion/sensation. Then there are preferences, which have representational content: they represent some 'goal' state of affairs that the animal deliberately aims to bring about.
Why is this important? Sterelny (TiaHW, pp.92-95) argues that, like decoupled beliefs, preferences increase an organism's adaptive plasticity, improving their ability to make apt decisions when faced with a broad range of possible responses.
For one thing, some biological goals are too complex to be captured by a purely sensory/affective drive (p.94). Consider social status in primates. There is no simple pattern of sensory stimuli common to all status-raising goal states for a biological drive to latch on to. Instead, the animal needs to be sensitive to a wide range of social relations, unified by functional properties that can only be tracked by way of abstract representation (cf. the Bennett quote).
Further, Sterelny suggests that drive structures are "winner-take[s]-all control systems" (p.93) -- "the strongest drive determines the action chosen, and at that point the other drives are epiphenomenal." To balance different motivators appropriately requires representation. (I'm not entirely sure why - there seems an air of stipulation about this.) When acting on your strongest preference, you can alter your behaviour in light of your other (lesser) preferences.
This would make sense if pure drives are defined as leading to involuntary/automatic action. Sterelny writes, "We digest, breathe, and vary out heartbeat rate without any cognitive representation of the metabolic needs these activities service." ('Situated Agency and the Descent of Desire', p248.) But our eating behaviour is more flexibly controlled, which I guess means that we act on a representation of our internal hunger drive, rather than the drive itself? We can certainly modify our eating behaviour in light of our other goals, so the behaviour isn't the result of any simple competitive drive hierarchy, at least.
I take it the idea behind this is that to engage in practical reasoning about a goal (e.g. sating one's hunger), one must represent that goal to oneself. Otherwise one couldn't reason about it, relating our beliefs about some possible state of affairs with our preferential ranking of that possibility. Drives are brute action-drivers, whereas preferences can combine with beliefs to produce more informed action.
Can beliefs combine with drives to produce intentional action? They might be guided by 'implicit beliefs' or information within the organism. But 'driven' action is not, I take it, a product of reflection or rational processes taking place within anything resembling 'central cognition'. (Otherwise I'm really confused about what "drives" are supposed to be.) Any such deliberative action must instead be motivated by preference-representations of the drives, rather than the drives themselves.
Does that sound right?