I’m not sure about that- I’m on my third company with extensive travel, and I am always expected to stay at the Courtyard-level hotels (it’s based on nightly rate, not actual amenity level, of course). And while I can expense a wifi charge when I have one, it’s pretty uncommon to have one.
The main exception is when I’m at a conference held in a specific hotel (East Overshoe Hilton Convention Center). Then I stay at whatever hotel is attached to the convention center, which is typically more upscale and often does charge a wifi fee.
My main point is not that business travellers are necessarily or even in the majority of cases staying at expensive hotels. My main point is that hotels that have a higher proportion of business travellers among their guests are more likely to charge extra for wifi, because they know that even stingy travel expense accountants will usually approve reimbursement of a wifi charge with no further hassle.