It seems that in the Star Trek universe, anyone with a half-decent warp capable ship can travel back in time by up to at least several centuries, just by travelling in an appropriate trajectory around a nearby star.
Given this, and given the fact that warp-capable ships are very common, I would expect time travel to be almost an everyday activity. For example, it could be used to gain a surprise attack in any conflict, to send warnings of impending doom, to make hoards of latinum by predicting the markets, or to change history for better or for worse. It probably has all kinds of other uses that I haven't thought of as well.
Although some of these things have happened in canon, they seem to be very rare, exceptional events. Is there an in-universe reason why this is the case?