Those buggers will just simply cut or saw off the rim of the steering and slide the steering lock clamp off.
as you said, steering wheel is just a deterrent.
better protection would be clamping the pedals. Proven. My previous car got broke in...they managed to by pass my RM2000 alarm system....and even managed to start the engine. but couldn't drive off as the pedals we locked together.
it's easier to cut the rim of the steering wheel than the pedals (pedals are made from harder steel).
All locks have their strengths and weaknesses. Even the pedal locks like the famous AutoLock Pro has a serious design flaw which allows people who know about it to pull out the lock without needing to cut or break anything. These flaws are fortunately not described in detail because we fear the wrong people would learn about them. Web sites might say something like:
"This lock can be twisted and turned in such a way that the lock can be removed without requiring us to cut or break the lock or pedal."
But they won't describe how they "twisted and turned it".
Pedal locks and steering locks are all deterrents because they make the thief work harder and longer to get into your car -- something that might dissuade the thief and to try elsewhere.
Anything that lowers the risks of car theft is always a good thing.
So saying things like "they can still tow away your car" is correct but not helpful. In the same way, we can also say "they can always airlift your car right out of the parking lot, so what kind of super car security system can stop that?"