Awnings make outdoor seating areas more pleasant by providing shade and blocking the rain. They also keep sun from pouring through windows, which reduces air-conditioning costs and protects furniture from fading.
Aluminum awnings don't require much maintenance, but they can't be ignored completely. And if your awnings are really old, they might benefit from a fresh coat of paint.
Fabric awnings need a bit more care than aluminum, but maintaining them well pays off in extended life.
Whether the awning looks dirty or not, rinse it off about once a year. If you live near a heavily traveled street that hosts diesel truck traffic or if the awning is under a tree, more frequent rinsing might be needed.