The worry for me is that without the lock it makes theft easier for pros who use low-loaders or those possibly towing the car away, albeit the alarm may need disabling. And then there is also the consideration about the effect on the insurance cover............ something to consider.
But as the key is still required to start the engine it is still relatively secure, hence why it is doubly important to make sure the kety(s) are always kept safe.
Agreed, the other option is try and pick a slu up when a car is being broken for a reasonable price.