Air carrier pilot reported; while waiting to depart; observing an aircraft that taxied beyond the hold short line allowed another aircraft to land; which resulted in a runway incursion and unsafe operation. The Captain reports unsafe actions at this airport on all his trips there.

Narrative

SGU is by far one of the most dangerous airports I have flown into. I have been there twice and both times the congestion of traffic is dangerous; often putting jet traffic into odd traffic patterns; with non-standard altitudes and unusual maneuvers in order to avoid other traffic and terrain in the area. On this particular day; we were attempting to depart between arriving and departing traffic. Aircraft Y was holding short of the runway in front of us. There were a couple of other traffic that were landing and it seems everyone was trying to expedite their takeoffs and landings to accommodate the six other planes in the pattern. Aircraft Z had just landed and as it was exiting the runway; Aircraft Y began crossing over the hold short line. Aircraft A then made a radio call that it was roughly a one and a half mile final. Aircraft Y continued to taxi onto the runway and then asked Aircraft A; 'do you have enough room'? Aircraft A replied that he didn't. Instead of continuing to taxi across the runway and get off the active runway the pilot in Aircraft Y said; 'okay. I'll hold short here'. Aircraft Y was already well past the hold short and almost to the runway markings. The landing Aircraft A proceeded to continue their landing with the other plane on the runway. After they landed they said that they don't call this the Wild West for no reason. To which another pilot replied with a 'yee haw'; further demonstrating how normal this behavior is at this airport.Both times I have been into SGU I have witnessed some kind of unsafe actions on behalf of other GA traffic in the area. Suggestion: This airport needs a tower.