why are couples scared of multiples?

💞SuE💞 • 39/ TTC#1 4 rounds of clomid at 25mg. 1 round of ivf/fet failed dec16. 2nd round fresh failed 14feb17. fet in april17
I'm a little confused here... I always loved the idea of twins. So when I meet childless couples ( like me) Not hoping for twins I don't get it. It is because they feel it's risky health wise? or just don't want it? I see it like this, all that pain after suffering, enduring <a href="https://glowing.com/glow-fertility-program">ivf</a>, the costs, the biological clock... and twins will complete my family nicely - all for the pain of one pregnancy, So I don't understand why people would consider fortis reduction. can someone shed some light?