Even if they're your biological kid, you get "I hate you! You're ruining my life!" before they steal your car. I don't know that that's much better. And it's about as true.
The problem is that step parents have zero legal rights. If the marriage or relationship doesn’t work out, the step parent loses their entire family forever. It’s a raw deal for people brave enough to raise someone else’s kids. I could only ever consider this if I were able to legally adopt. That way, heaven forbid, things don’t work out with the relationship, they’re still my kids.
On the bright side, you have the exact say on the kids you raise when they aren't yours. If they are biological, you are stuck with whatever hand you are given. So if you don't like their kids, you can leave with no issues. A family you choose can be better than a family you are born into.
Although yes, childless is the better option for some of us.