1. This would cause more problems. People would forget what levels skills become available, and berate new players or levelling jobs for not using skills they dont have, or abandon low level duties because they got paired with newbies.
It would also likely lead to more skills beibg distributed at higher levels, making actual low level jobs even worse.
The solution is to distribute more skills at lower levels to make those levels more fun for everyone, not just those at max level.

2. ..why? So you can save a couple extra gil?