Even if they give an xp/h boost at max level, lots of people don't skill that much after maxing.

Instead , the ones that affect xp rates and such are so rarely purchased because they are a bad use of points compared to the very meaningful combat auras - vamp, penance, the damage and accuracy ones are all super important for a lot of types of pvm but take so long to get that its almost never worth buying the skilling ones, BECAUSE xp rates are so high anyway that to get to max they aren't necessarily that important compared to the utility of combat auras later.

If you plan to go to 120 or 200m or are doing pets, it might be worth it, but the benefits they give aren't worth the amount of time it takes to get them.