Good question. Since checks are usually torn out of the checkbook along the perforation created to facilitate this action, "cutting" is unnecessary.
It should be called "tearing" a check, or the verb should refer to the writing of the check, rather than the method used to remove it from the checkbook.
On the same subject, why do people say "try and" when they mean "try to", or they say "ramp up" when they mean "amp up." When something goes UP a ramp, it LOSES momentum, which is the exact opposite of what they intend the phrase to mean. When you say you will "try AND" do something, you are promising to try AND you are promising to get it done. "Try to" simply means you will make the effort, but you are not promising success.
The point is, people say all sorts of things that make no sense, and they never think what they are really communicating when they say these things.
There will probably be someone who reads this and mumbles "I could care less," when they should say "I COULDN'T care less." I hear that one all the time.
It gets annoying, especially when I hear highly paid journalists doing the same things or pronouncing "jewelry" as "jewlary" or "realtor" as "real-a-tor." They should know better.