Why is time travel so rare in the Star Trek universe?

Question

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?

Answer 1

There are temporal agents such as Daniels (Enterprise) and Braxton (Voyager) that actively monitor the timeline to search out and correct any temporal incursions. So you may be correct that different species are regularly attempting the sling-shot method (and others) to time travel, but perhaps their efforts are repeatedly being thwarted.

Answer 2

Time travel, throughout the star trek franchise, is such a common story plot, we should be amazed why anyone even bothered writing the temporal prime directive. Seriously, we're talking about more time travel than the Terminator franchise!

If you look at the history of star trek episodes, time travel story plots may be the most popular one for the show's writers. There are 50 different episodes across the shows, not including the movies, where there was some kind of time travel involved.

https://memory-alpha.fandom.com/wiki/Time_travel_episodes

Now, to answer your question, the only time you see any enforcement of the temporal prime directive, are in the Voyager and Enterprise series.

In Enterprise, you see the appearance of Daniels, a time agent that starts off undercover on the NX-01 to find out who in the temporal cold war has gone back to try to disrupt the time of the founding of the Federation.

In Voyager, you see the appearance of Captain Braxton and the Timeship Aeon. This is probably the best use of temporal policing, as you see in episode 5x24. Seven of nine was pulled from one point of the timeline where she is about to die, and used as an agent to thwart another disruption to her timeline.

This is probably why instances of stopping the timeline disruptions go unnoticed. Because time agents recruit people from that point in the timeline to stop infractions, which offers the lowest impact possible.