1. Trying to get more money, driving by a few times, waiting till person is so desperate, that he/she will pay moon prices while meter is off.
2. 'Too far', 'too much traffic', cannot use "highway".
3. Short tours bring in more (10× 35 baht short-distance base-fare, say, total of 1.5hrs.) than 2 long-distance tours a 45min. (dunno, let's say 2× 130 baht). - In the first example, much less driving (incl. return trip), and no 'having to guess where places are', and 90 baht more (not incl. multiple tips). And, of course, they get away with it!