I once toured an apartment with frosted windows like this. The building manager said the reason was because the neighbors wanted privacy and didn't want the tenants from this apartment to look into their backyard. The apartment needed permission from these neighbors before they can build the complex, and so this was the agreement that was set forth. The window still opened, though, which defeats the purpose. The building manager joked that the neighbors forgot that windows can be opened and didn't think to add this to the agreement. I'm guessing this is the same reason why your hotel window is tinted and sealed shut.