Note that Google and the other route finders have not actually driven the routes. They are simply connecting 2 places. Sometimes they get it right - but they can also offer very bad advice.
As an illustration, I am going to show you a Google search for a route by car from Swansea to Cardiff Airport. Nobody who knows the roads in this area would follow such a route. It starts off well - heading east along the M4 (which is like an interstate) but it is when it tells you to leave at Junction 34 that things go really wrong. It actually sends people for a few miles going south along country lanes before reaching better roads to get to Cardiff Airport - coming in from the east whilst you started your journey in the west.
So, those interested might like to click this link - which will bring up the route. Then zoom down to the bit where it heads south from the M4 and drag out the yellow man onto the country lanes and you will see how Google have really goofed up. (I have even come across trucks/lorries on this narrow country lane through the village of Pendoylan).
PS. It might be better to use real maps just like the good old days!