The point is that if a security guard is prepared to take a bribe to allow goods onto a plane, where exactly does this stop? A few small bottles from the hotel does not matter, but what about, well anything that can be used to blow up or hijack the plane?
This was my first visit to Egypt so regulars may get used to the system, but baksheesh seemed very much like a bribe to me. It goes further than a tip; you are,for example, not allowed to take your camera into the Great Pyramid, but a little money changes hands and you can, then inside another official takes a little more to take your photo.