Surveys can be deceiving. For example, if you broke it out by the class of hotel, I'm sure you would get much different results. I would bet that 10% of customers tip at a Hampton, but probably more like 75% at a Sheraton. It's about the class of clientele.
In addition, you skipped past the key part of the article: the tipping guidelines from Emily Post that tell you to tip the maid unless it's a one night stay at a motel, not a hotel.
If you're staying at Days Inns, then yeah, you probably don't need to tip the maid. They really don't expect it from people staying at that kind of hotel. But if your airline puts you in a Doubletree, then not tipping is going to stand out, and the airline crews are going to get bad service because of it. Hotels tend to put airline crews in the same rooms every night. They block them off and don't sell those rooms to the general public. If a maid consistently gets tipped from regular business travelers, but doesn't get tipped from airline crews very often, I wonder whether that maid is going to replace the sheets every night, or clean the drinking glasses? I'd rather not find out and just treat them well.