EDIT: after missing offtopic.
Most of Harem hotel data is in 1080p image files. All those costumes and image loop animations add up and game has some space wasters like empty Kali's room or raw png images used in scenes.
To be fair, Kali's empty room is a single image, and would account for very little of the games size.
Outfits are a different issue, but then, if we did not have outfit options, there would be people screaming for outfit options, which does play a larger part in the file size of the game.
Overall though, the events in the game are by far the biggest reason for the file size. The game has a lot of side content, most of which helps establish the characters and their personalities.
A lot of people really enjoy that, and how it builds not just our understanding of the characters, but of the world that they live in, in general.
So, taking out that content, is really not an option, because Harem Hotel would not be as good as it is, without that content.
Harem Hotel is not like most of the visual novels on F95.
It is a detailed story that just happens to have sex and harem content, and bare bones minimum game play to it.
No grinding, and no searching around rooms for things to click on.
Nothing more than a few simple riddles with answers that can be found on Google.
Think of it as the naughty version of War and Peace.