Why doesn anyone use the wormhole in later seasons?
Well, in Seasons 1 and 2, there are hints of a powerful empire somewhere in the Gamma Quadrant, an alliance of worlds like the Federation, but an “evil” version. We finally find out about them properly in Season 2’s finale “The Jem’Hadar” and Season 3’s premiere “The Search”. They’re called the Dominion, and they consist of several “tiers” – the military, who are a genetically engineered race called the Jem’Hadar; the Vorta, another genetically engineered race who control the Jem’Hadar and organise the political side of things; and the Founders, who are the leaders of the whole thing. The Founders, much to Odo’s chagrin, are the same species as him – Changelings or shapeshifters. The Dominion objected whole-heartedly to people coming in and out of their territory all the time, so they blow up a Galaxy Class Federation starship (a very big and powerful one that took a long time to make, and would no doubt annoy the Federation if it got blown up). So, wormhole traffic was kind of limited
