The quarters at the home is also a command center where agents on duty are and probably where they monitor the grounds and the walls from. That is why they build fences and increase security at the homes of Presidents. To make it easier to guard them. Where the agents spend their off time is not the same as where they spend their time protecting someone at their home. In the case of a ranch, having a place to sleep means they don't have to leave the grounds when they are off duty and travel 30 miles to a hotel. They would also have a command center at a hotel when a protected person travels but it isn't a room for agents that are off duty to sleep at.
The biggest issue in this is the lies told by the Trumps about how they didn't charge for the rooms or only charged $50 and then it turns out they were likely charging the same or higher rates than other guests.
