Why can the aircraft not turn on pitot heaters itself?
There's much simpler and safer logic. Most modern Western transport aircraft automatically switch the pitot heaters on when in flight mode or at least one engine is running. Pilots can manually force pitot heat on, but there's no direct option to switch them off. Normal procedure is to leave it in auto.

Boeings since the 757/767 are automatic (exception: 737), and Airbus has had it automatic since at least the A300-600. ERJ is auto, not sure about the CRJ200, but the 700 is auto.

Pitot heat indication systems are already required by certification standards. 14 CFR 25.1326:


  If a flight instrument pitot heating system is installed, an indication system must be provided to indicate to the flight crew when that pitot heating system is not operating. The indication system must comply with the following requirements:
  
  (a) The indication provided must incorporate an amber light that is in clear view of a flight crewmember.
  
  (b) The indication provided must be designed to alert the flight crew if either of the following conditions exist:
  
  
    (1) The pitot heating system is switched “off”.
    
    (2) The pitot heating system is switched “on” and any pitot tube heating element is inoperative.
  


EASA CS 25.1326 is basically identical.

The Antonov 148 is certified to EASA CS-25, so it must have had such a warning system.