Thanks for playing!
Some skills have lower caps right now - each activity that can increase skills only increases it up to a certain point, and not all skills have higher tier activities available so far. Gathering can't go any higher than level 30 at this point in the game. Eventually I'd like it to be possible for all skills to get to at least level 50, if not 90, but it might not be in Graham's destiny to be a Master at everything.