I'd say age does matter, since people use this as a measuring stick to see where they would address you. How they would deal with you. A physician would definitely use age as a starting point in his diagnosis. But still why do we use age as a template to see where someone is in their lives?
He's 40 and still single? Something must definitely be wrong with him. He's 35 and still living with his parents? He's 75 and still working? Why didn't he save up for his retirement? The mere mention of age tend to make a lot of people make these immediate assumptions and prejudices on others.
By no means is age a sign of maturity, true in a lot of cases but not a be all in everybody. I still see a lot of old folks acting like spoiled brats, throwing a tantrum just to get their way.
It is so subjective- age. How can we contain someone to a pigeon hole and say you're 30, you should be this and that? Were there guidelines when you reach each year as you get older?
Why do people use age as a starting point to gauge on how to treat you? Why will they treat you differently if you are 20. I will let you use the electronics if you are 30. You may use the kitchen if you are 40. It really is immaterial whether or not there is a number there or not. If the number is immaterial then why should it matter if the matter isn't there.