The routine I'm working off has me doing two upper-body lifts, one-lower body compound lift, and one upper-body accessory lift twice a week; and one upper-body lift, two lower-body compound lifts, and one lower-body accessory twice a week. And then there are two days that I take to mean, "eh, do whatever compound/accessory work you want." (Those days are supposed to be structured around cardio, but I get enough non-gym work there that it's like, whatever.)
I mix the lifts up every five weeks, so maybe for one cycle I focus on improving 2 count-pause bench press for one of the upper body compound lifts and then for the next five-week cycle I focus on the close-grip bench instead. Keeps me from getting bored. (I ran the same routine for three years at one point without any progression. I don't know why I was convinced that programming didn't matter--it does!)
Might have thought it didn't matter since in the beginning it probably isn't super important at least things can be simple.
It certainly can become useful to mix things up after a certain point. Even simple stuff like doing low reps heavy one day and high reps light another. And then people who are more advanced will often get a lot more complicated.