You are thinking about this as a local golfer who is playing the course for the day and heading out. Consider a golfer staying onsite.
Once you have significant onsite accomodations, as they are doing with the cottages, then you will need a clubhouse with more food and beverage options. Golfers staying onsite will want to be able to get everything right at the resort, especially if they are playing 36 holes per day. That is the case at high end golf resorts here in North America, like Cabot Cape Breton, Streamsong, Bandon, etc.
Those resorts are set up so that you can visit for several days and never leave the property, and in some of those resorts there are very few options for eating nearby. That is less likely to be the case at a place like Castle Stuart, where golfers will likely be traveling to other golf courses, but some golfers may use it as a home base for a few days in the Inverness region while playing Dornoch, Nairn, etc. So once they are done for the day and come back to their home base at the resort they will want to be able to get a nice meal at the resort, and a bar to have a few drinks and a good time after dinner.