Eh, I don't mind the system I grew up with:
16 - Consent / Learner Licence for Driving
17 - Provisional Licence for Driving
18 - Drinking / Voting / Gambling / Anal Consent (this is actually a law in my state)
20+ - Full Driver's Licence
The ages for Licences are just the minimum age you can get it assuming that you start your Learner's process as soon as humanly possible.