In my experience, it was because I didn't know any better. Honestly.
I used to rag on Android, in general, and Samsung, in particular, because I didn't know any better. All of my experiences had been with very early builds on low-end devices. In fact, I wouldn't have gotten my S5 if my L925 hadn't taken a swim in the Mississippi Sound. My love affair with my Samsung TV didn't hurt, either!
I think that's the thing, though, is that it's a phone that has to be lived with to appreciate it. It took me a few days to warm up to it, after my trusted sales rep sold me on one. It met my requirements: Water-proof, powerful, and with a decent camera.
Do I miss Cortana? Absolutely, but I don't miss the walled gardens that Microsoft and Apple keep their customers in with their operating systems. I've customized my S5 so much that it's way easier to use than even WP, which is saying a lot. I wonder if that's the problem, that reviewers can't live in the review models. Bias is a part, too, since so much of my opinion was informed by pro-Apple tech sites or other WP-users. Me, though? I'm loving my S5 and I don't regret it.