Why do people make a big deal about this?

When someone is 17 they treat them like kids but when they are 18 they suddenly become an adult when there is little difference between them.

In most places 17 year olds can consent to sex with anyone and drive a car, go to military and have the capability to do everything 18 year olds can mentally and physically.

I don't see any difference between 17 and 18.

Why do people make a big deal about this?
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