Better questions would be:
Why do the northern ETZ states extend so far into what should be CTZ? Indiana and Michigan should easily be in the CTZ.
Why does the CTZ extend so far into what should be MTZ? Everything west of Brownsville including all of North Dakota should be MTZ.
The Utah/Nevada border is pretty close to where all of the M/PTZ line should be. In Canada the MTZ extends west into what should be two more zones - past the Pacific into another so it borders the Alaska time zone. So when crossing from Canada into the main part of Alaska you are moving the clock not one hour but three!
See this map that has lines showing the longitude lines that should be the baseline for TZ lines:
Current local times around the world, including (DST) changes.
www.timeanddate.com