At one time, musicals were so loosely constructed that you could easily insert additional numbers by most any composer. Today, every song in a musical should serve the story. To do this, songs must be clear enough for an audience to grasp on first hearing. Creative and entertaining use of rhyme has been a hallmark of musical theatre since William S. Gilbert's deft couplets left audiences laughing in the 1880's. Rhyme is one of a lyricist's most potent tools, especially where comedy is concerned.
Creative rhyme is important in any type of showtune.
At today's ticket prices, people have the right to expect a smooth, professional effort. Of course, the witless scores of Footloose and Saturday Night Fever prove that some audiences will tolerate anything if the volume is deafening enough.