I don't know whether there is any point as such but they are different to other spaces in that they can be built on but do not have swamp tiles placed on them at the start. I guess they just provide easy building places for the start. (I've not played the game so don't know how they affect gameplay).
They are there simply as building spaces at the start of the game. So if you wanted to build straight away you can. I think this is a great game, though the Palace looks a bit space-age on BSW. Handy hint - when the treasure bag is empty you can trade one of yours in, before you build, then win it back again when you build next to your gondola. Don't do this if you are not master builder as they will get it. :-))