Barrier protections are great - but have one of the highest perfect use condition failure rates against pregnancy. If you used them under perfect condition correctly every time there's still a 2% chance of failure every time...

Typical use however like, people hurrying, using bad technique of application or removal, improper sizing, not inspecting them before use or using expired product or other sundry defects of the condoms themselves means condom's real life failure rate condition is about 18%.

Not to knock the condom but it's not foolproof. Even paired up with the pill which has a decent track record when under perfect use conditions but one of the highest rates of imperfect use because of missed or improperly timed doses you still are rolling the dice.

Let's lay some ttrpgs here. Everytime you have sex under that pairing it's like you are rolling two individual dice. Let's take the typical use of condoms and the pill. Roll a six sided die to represent the condom and a 10 sided die for the pill. If both die show up with a 1 then you get a pregnancy. Not bad odds until you realize this is repeated every time you have sex.

Adding another die to the equation in the form of a hormonal birth control for the other partner alters the chances to be more airtight. Also sometimes you as the male partner might want assurance because you generally don't know of your partner is taking their pills right.