I beg to differ. Of course you have immature older people and mature younger people, it's just generally the younger you are, the more immature you tend to be. Prove me wrong.
you disproved yourself when you admitted that age does not always equal maturity though.
but i can always use the example of my school where practically everyone there acts like kindergarten students despite considering themselves to be adults (even the 13 year old) which shows that just because you're older doesn't mean you're mature.
this was especially exemplified when half of the senior class at my school straight up vandalized the school and then pitched a fit when criminal charges were placed upon them because they considered breaking in, spray painting walls, covering up security cameras, releasing live creatures in classrooms, flipping trash cans, and peeing on furniture etc. (the list of what they did is much longer) to be "just a prank" that does not warrant punishment. essentially, they refused to be mature adults who would accept punishment for what they did.