Star Trek has been a staple in the science fiction genre ever since Gene Roddenberry first brought the spacefaring sitcom to audiences in the late 1960s. Since then, it has spawned various movies and TV shows that are still being added to today. Throughout the years, it has come up with some truly spectacular what-ifs. These range from technological innovation like the faster-than-light warp drive and the matter replicator, to a plethora of diverse (if not mostly humanoid) alien races.
Among these alien races are the omniscient and often nefarious Q — a race who are all called Q within their society, the Q continuum. One Q particularly enjoyed tormenting main protagonist Starfleet captains, appearing frequently in the franchise. Of all these, however, he chose to leave Captain Benjamin Sisko of Deep Space 9 alone. But why?
The in-universe explanation is most likely to be summarized by how he probably did not find the morally questionable Sisko as interesting as Picard or Janeway, the other two captains he frequented over the years. The Q are an interesting lot, and it’s easy to forget that the actions of the Q played by John de Lancie are not representative of the whole race. His actions were often extreme and got him in trouble with the rest of his people, but he only did what he did because he was bored. This was the trouble with being immortal, timeless, and omniscient beings: eventually, they experienced everything there was to experience, discovered everything in the known and unknown universe, and philosophized their way through every thought and query possible. This got so extreme that at the point audiences meet Q in TNG, he remarks that they don’t even talk to one another more, as everything has already been said.
Q's boredom resulted in his mind games thrown at Picard and Janeway, but while his actions were always masked with the facade of testing humanity or proving a point, they were ultimately because hewas bored. What made Sisko interesting was that, ironically, he was not interesting — at least not to the trickster Q. Q was a troublemaker, and most of the time acted like a child who wanted attention. Picard and Janeway took the bait, much to their own and their crew's detriment, acting in their own distinct ways as parents dealing with a child having a tantrum. They broke all the rules of the parenting 101 guidelines, reacting and engaging with his actions, but most importantly gave him the attention he so badly desired.
This was almost a guaranteed response which kept him coming back time and time again to wind up his ‘parents.’ The most oddly twisted part of this was that not only did this god-like being behave like a child for attention, but he genuinely started to treat Janeway and Picard as parental figures. During Voyager and TNG respectively, he would come to them when he needed help with fights he had gotten into in the universe playground, and when he was having issues with his girlfriend.
Sisko, meanwhile, was a man unlike any Starfleet Captain audience had seen before. The whole premise of DS9 was to be a gritty exploration into the darker underbelly of the Federation, holding the microscope up to the planets and people that Starfleet simply did not have the time for. Despite, or perhaps as a consequence of, Sisko being the only real-life parent out of the three examined captains, he was also the least parent-like of them. He was strict and took no nonsense, and had no time for any of the shenanigans Q was pulling. He had no interest in the being, refusing to entertain him, and thus Q didn’t get the gratification he was looking for.
Sisko doesn’t try to adopt any moral high ground, outsmart Q, or even try and teach him anything. Rather, he simply sees Q as the child-like bully he is and refuses to be tormented by him, resulting in what might be one of the most satisfying moments in Star Trek: Sisko grew so tired of the evasive and childish ‘god’ that he just turned around and punched him in the face. This is something that Janeway or Picard would never do — just as a parent never would, or should, do to their child. Sisko's action instantly took away all of Q’s childlike attention-seeking power. He even says this, just like a child would just after getting floored: “Picard never hit me,” to which Sisko replies, “I’m not Picard.”
While some fan theories suggest Q was afraid of the prophets, being potentially as powerful as he was, the above reasoning is regarded among fans as the most likely. There is also an out-of-universe explanation for Q's reduced presence in DS9: that his character wouldn’t have fit so well within the grittier storyline, and wouldn’t have worked in conjunction with the much more down-to-earth, no nonsense, realistic characters. It may have also been because DS9 writers simply got tired of writing him into the narrative, unable to think of any interesting stories to give him that hadn't already been done. This being said, Q's semi-villainous return in season two of Picard was a treat. It was a great way to say ‘Bon Voyage’ to the Star Trek icon.