Without being graphic, having something so large pass through a birth canal that is usually a lot smaller can have lasting physical effects (but not always!)
your tummy sees the light more (summer, beach, etc) than the other part you refer to. So if you care about cosmetics I'd wage people would go for something that does not leave a huge scar over their guts.
You're comparing a surgical scar in your abdomen (which these days can be done pretty minimally invasive in some cases) to unpredictable tearing into the perineum (and in extreme cases even into the rectum), not to mention likely complications from birth like (temporary) incontinence.
I wouldn't advocate for routine c-sections and it is still surgery with all the risk that entails, but if you're not generally prone to scarring, the optimal outcome for a c-section can be far more predictable and doesn't have to involve a "huge scar over [your] guts".
