this might be a dumb question

but i see a lot of moms wearing oxygen masks during labor at some point or another, and i was just wondering what are some of the reasons that would cause you to need to wear an oxygen mask? idk why but seeing an oxygen mask on someone makes it look like there’s something seriously wrong and it just makes it look 100x more scary!! again, sorry if this is a dumb question. i’m a first time mom due in 9 days and i’m just trying to understand as much as i can!