The big issue tends to be complex logic for going to sleep often getting stuck. Ie. "oh, I was trying to use the LTE connection to poll for updates, but the connection got reset so I kept the CPU awake forever whilst retrying every 5 minutes rather than going to sleep mode".

Older cars had this too - I had a bunch of cars which would kill their own batteries if not locked - the engineers assumed that all owners lock the car when walking away, which often isn't the case in your own garage.