Currently, due to the ability to inject skills via SNI, you can have skills blocked where the effective skill level is higher than the blocked level.
For example: you can have level 40 of a skill which is blocked at level 20.
This is an anomaly new players cannot achieve as SNIs are no longer generated.
There is no incentive for a player with elevated levels of Skills to unblock them, this is especially true if a player has injected skills to a very high level.
Suggestion: a player's skill level should not be their effective skill level - it should be their unblocked level.
So if a player has level 40 of a skill which is blocked at level 20, they will act as if they have level 20 of that skill. The player now has an incentive to earn the P.Notes required to unblock the 20 levels.