Cole Phelps has to wear his badge tightly, because Canterlot Police Department is a lot more cutthroat than LAPD was. Rightfully so, as the underbelly of Canterlot is nothing but criminal scum waiting to be brought to justice, by any means necessary.

These cases are much different than Cole had to deal with in the past, maybe it has to do with the new pony body or maybe it require different skills that Cole Phelps simply don't have, so he hires some help along the way. They might even prove to be useful, because hard wit and cold evidence can only get a detective so far.

You just need a touch of friendship to make the worst criminals crack.