There's actually a few different types. Some are single choice if, at the start of chapter 3 I think, you chose to not display any options that will lock out the Macy/Denise paths. In that case, the other choice would have been a lockout choice, and that's hidden on the players request. On some occasions, you might have some options not available because of previous choices or stats, and that could leave you with the one.
Finally, there's a few where there's a one choice option because I wanted there to be a pause, and for the player to "go" the action, whatever it is. You're not alone in that some have complained about it as well, and I've tried without it but then the rhythm of the scene just feels... off to me, if that makes sense. It's just texts and events that keep coming leaving the player too much of a bystander.
I do think that renpy is annoying in that you'll happily be space-barring away through dialog and all of a sudden, choice! Find your mouse with your other hand, track the cursor, click. Then back to the keyboard. To alleviate it, I've added numeric hotkeys to all choice options, so really your hands (neither of them
) will never have to leave the keyboard; even rollbacks can be done with pgup.