Agreed, but it's not a positive enough of a retention to hold the tire under race conditions. It's OK to do that to limp home, but I certainly wouldn't start a race in that manner. A system to positively attach the tire to the rim would be a good idea. Gluing does work in most situations, but by it's very nature, it's meant to be removable. Tire pressure is also not a the perfect answer because in some situations (cyclocross) the entire reason you run tubulars is to be able to run reduced pressures (without pinch flatting). This would reduce the effectiveness of that form of retention.