If we are debating automated pitot heat I’ll chuck into the mix that on some types it’s any engine engine running = pitot on....(with an EICAS message if it fails).
Having the trigger for heat being handbrake release means the probe heat is on for towing ops, which may not be desirable on some types and certainly could get messy if the aircraft is towed for maintenance purposes with the covers on...
Having probe heat being turned on at a particular thrust setting above idle could IMHO cause probs in icing conditions on the ground or early on in the takeoff role....on some types on the ground you only nudge the power up to start taxiing, most of the time you are taxiing with the thrust back at idle.