Tours and resort activities, e.g. scuba diving are rarely credited with points.

A big question sometimes is spa services. I don't often request therse, the wife does, but I can tell you at least with certain Hyatt properties, on site spas sometimes do not credit such services as point earning. Can't say for sure that this is an issue with Marriott, but forearened is forearmed!

In addition, SPG routinely does not credit one with points for parking, so this too, may occasionally not show up as earning on your bill.