They should also provide each user their own 'custom' canary.
Unfortunately that's entirely impossible in the current situation. The canaries that are currently use, or used recently, have to be very carefully constructed to avoid removing it breaching the laws regarding the secrecy of the orders. Apple's view, at least until recently, was that disclosing that they hadn't received any, for anyone, was generic enough as to not breach secrecy. Doing it for individual users would be about as legally sound as phoning the user up and warning him that the Feds are after him.