The casino has made damn sure that there is no line of sight to the outside, so she won’t know when it gets light.
A key element of the vegas experience, along with the free drinks while gambling and the lack of clocks on the wall. Time does not exist here. This is what draws Ben here - not to gamble but instead to drink himself to death with no possibility of anyone noticing and no possibility of not being able to get alcohol because of what time it is.
