Hi Wokka, Yes l agree 100% with you that all Reptile enclosure with heat lamps built inside them just like mine are, should have light cages to help prevent the Snakes, from wrapping themselfs around the light bulbs.
The reason why mine don't have any light cages installed is because none of my enclosures have Thermostat connected to them, this stops the lights from turning on & off. so there is no chance of my Olive Python's from wrapping themselfs around the light bulbs.
The way l control the temperature inside my enclosures is by using a lower wattage light bulb, during the day l use a 60watt clear reflector light bulb, and at night time l use 2 x 40watt red party light bulbs during the summer months, but in winter time l use 1 x 60watt and 1 x 40watt red light bulbs.
The 60watt clear reflector light bulb is connected to a dimmer so l can turn it down without turning it of or changing the reflector light bulb.
Not once have any of my Olive Python's tried to wrap themself around any of the light bulbs day or night, like you said in your post l Dragon_77 ( Les ), have plenty of experience in reptile keeping which l do but l still am learning just like you and any other Reptile keeper is.
l got my first pet lizard which was a Eastern Blue-Tongue in 1975, and got my first snake which was a Children's Python in 1989, so that is to let you and others out there know how long l have been keeping Reptiles for.