It's pretty clear if you read what there is to know about the history of Karate, that kata were intended to impart combat lessons.

Like Duane said there was some modification when Karate got mainstreamed, but generally it's accepted they were made to impart certain combat lessons, rather than as meditation, an aesthetic form etc. That stuff came later, with introduction to the school system, and to mainland Japan. One of the differences in older Karate also was that people generally knew fewer kata, and (this is my own opinion) two man practice played a more central role.