Same here in Michigan.
Here in Michigan it is a way to give local control to the residence within that division of the county, without actually being incorporated into a city proper. For items such as roads, Services, zoning, enforcement, trustees, Etc. A Township can also incorporate to be a "Charter" Township, giving it the same legal rights as a city. With many townships in Michigan, you also have an incorporated city somewhere within, or even splitting its border with another Township. Often, services are consolidated within the city and the township together. In my Township, Water and Sewer services are provided within the city limits (small village where the post office, Banks, and schools are located), but those of us out in the township are on well and septic. The city can attempt to Annex, or grow into the township, as long as those residents in the potentially growing area vote to join the incorporated city limits. Then those residents would be afforded the city services like sewer and public water, Etc.
One area in particular that is an advantage in my Township, relates to zoning and land-use. Within the city limits, they can carve out a residential lot anywhere big enough to fit a house. But in the township, a residential lot must be at least 2 Acres or above. That helps to limit the expansion and sprawl.
Regarding other services, the Township Board of Trustees, who are voted in, can choose to either pay the local city police and fire to service the township, contact (thru mileage) the county deputies, or skip the deputies and rely on the state police which are few and far in-between.
On the flip side, the taxes in the township are cheaper than the city, but then again, we don't receive City water or sewer (that's fine, I actually prefer my well water to city water), garbage collection (must hire our own), etc. Trade-offs