Are babies actually THAT hard?

So I post a lot about how obsessed I am with getting married and pregnant as quickly as possible or pregnant by someone who will stay around or anything.. every time I post I get all the responses about waiting and loving relationships and how hard it is etc... and I'm just wondering is it actually that hard? I see happy single parents all the time I see happy couples with babies all the time. I don't see how a relationship would get harder with a baby, I mean how can someone be unhappy about a baby? Maybe I'm naive but I just don't get it I don't think it is really that hard, I don't think I would struggle. I feel like again, my life is very together except the singleness and no baby. Literally my life would be perfect if I had those 2 things. I just don't understand people I guess because I don't see it being difficult even financially I don't see how it would be hard. I have seen people I went to school with who are poorer, not in stable relationships, or just overall unstable who have kids and partners and seem reasonably happy.