We don't know that. We can only speculate.
Consider that ordinary events (as opposed to "historical" ones) are lost quite quickly in all societies. The written word is the most valuable and missing ingredient of human history. About ordinary events.
This has been referred to as "silent evidence" or "silent witnesses." Consider that thousands of man-hours are commonly spent going through garbage piles barely 100 years old to try to reconstruct the ordinary lives of ordinary people. If permanent written records were available all this wasted time would be unnecessary. That underscores the simple but crucial value of things like literacy rates and permanent recording media.
Sure, the mechanism might have been used merely to cast horoscopes --- or not.
The reality is that we can only speculate; we don't know, and might never know.
A mechanism that computes the positions of the planets can be used for what other purpose?