It seems like such a random-ass place to put a freeway before any connections existed.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fsnag.gy%2FNWUXkC.jpg&hash=f7b1c2ff6781c20676c45cbd9f9e519ab4518128)
Traffic flow by the Chrysler HQ and some of the plants during WWII. The Willow Run Expressway was built for much the same purpose (traffic flow to/from the plant) during the war.
To get from one side of Detroit to the other more quickly it was due to heavy traffic and was the only street to cross Highland Park. It functions as a link between I-75 and the Lodge though.
It was also proposed to extend east to I-94 and west to I-96 back in the day.
There is information at michiganhighways.org, including these entries:
M-8: http://michiganhighways.org/listings/M-008.html
M-14: http://michiganhighways.org/listings/M-014.html