Knock, Knock. Who's There? You love Dopamine!
Who doesn't love Dopamine?
Dopamine is the neurotransmitter essential to motivation, learning, and the brain's reward circuitry - in other words, enjoyable activities will cause a rush of dopamine into brain areas already primed for reward/pleasure.
Dopamine - it encourages sweeping.
Hopefully not to the point that a sweeping habit becomes a serious problem.
It is also happens to be essential for what we consider regular movement that might get us to pleasurable activities - even if that just means getting to and sitting down in the office chair in front of your PC. Deep within the brain is the basal nuclei, which control movement in an inhibitory fashion. They will inhibit muscle tone, turn off useless/unwanted movements, and coordinate slow contractions like ones associated with posture and support. The best example of what happens when this is not functioning normally is Parkinson's Disease. Gradually the useless and unwanted movements of the body are manifested in tremors, and rigidity of the muscles, often those associated with posture, make it hard to initiate and follow through with new movements (like getting in and out of a chair as quickly as one is normally used to).
TL;DR - Dopamine makes fun activities fun and voluntary movement into/out of desk chairs less tasking.