Lennon's name might be in the credits for "Why Don't We Do It In The Road," but at that point in the Beatles' career a songwriting credit of "Lennon & McCartney" was more accurately "Lennon OR McCartney." I'm pretty sure that Paul deserves all the credit (or blame) for that one.
Almost all of the Lennon-McCartney songs were one or the other. Let’s Do It In The Road was all Lennon though it still carried the Lennon-McCartney credit.