Pull out method is a less viable method of preventing pregnancy, and especially less viable at preventing STDs. However, it's still considered a contraceptive strategy.
For every 100 people who use pull out method perfectly, within a year, 4 will get pregnant. Since not everyone does a great job doing it, in reality 22 get pregnant every year.
For a going-steady couple that isn't worried about STDs, keeps an emergency contraceptive ('morning after pill') ready for oopsie mistakes, and live in a country that grants women bodily autonomy (or have discussed and accepted that a mistake might lead to a child), pullout is a perfectly valid contraceptive mechanism. There are better, but considering that basically every method except a condom/internal condom can cause extreme discomfort or bad side effects to the woman in the relationship, I think it's totally fine to choose pull-out.