Thinking the answer is simply monetary - they charge you because they can. Must be enough suckers that are unaware of/don't read how much hotels charge, or don't care because cost is expensed.

The same goes for hotel wi-fi, many hotels charge more per 24h than monthly cost of mobile internet, cost waived for elite members.

The exception to this nonsense charging still seems to be TV. Although the actual cost for the hotel is considerably higher per night, the use of the 55'' flat-screen TV does not result in any extra charge