Why is correct autorouting so difficult, Garmin?

3 examples from a tour in Austria last weekend:

1. Route from „Langenlois“ to „Nöhagen“:
   green = autoroute by garmin
   orange = simple direct way
2. Route from „Melk“ to „Wieselburg“
   green = autoroute directing me on a minor road directly near the highway connection!
   note: no „highway“ or „toll road“ avoidance activated in the settings!!!
   orange: simple direct connection to the highway
   
3. Route from center of „Mariazell“ to „Neuberg an der Mürz“
   green = Garmin directing me on a very narrow, steep street in the city instead of leading me on the main road (orange) to the exit of the village
   

navigation device: zumo660 (current firmware)
map: city navigator europe 2017.1