On a couple of occasions I've landed a raft on shore, gone to do something – usually visiting a riverside village – and forgotten exactly which square of the zoomed out map I left it on. I then have to spend about 5+ minutes searching around until I found it. It's like if you lost your car in a parking lot at a very large store, but Iron Age edition. To avoid this, I've taken to marking them on the F6 "super-wide-view" map with a marker tagged "parking" but then one has to remove them again when you leave or else that map gets cluttered.
It would be a small playability kindness to players to have raft visible on the zoomed out map, like shelters are. I would say if there is a square with a raft and a shelter, then the shelter would take precedence in being displayed, and be the only object shown. You're less likely to forget if you left your raft at the shelter square.