Take into account that the film was made in late 1970s, when every major Hollywood studio and its grandma tried to exploit Star Wars craze.

Even more importantly, the film was made for the fans of the original 1960s TV show, who had to use a lot of imagination when watching adventures of USS Enterprise on small screen, being made on the cheap (with some episodes recycling props and locations form westerns and period dramas). Film producers simply felt obliged to show anyone that they were able to make a proper epic big budget film and the easiest and simplest way was through long scenes when nothing actually happens but a fanatical trekkie could witness millions of dollars being spent on special effects.