Well, so many reasons ... until 4.0 the whole framework was ugly and the tools were very immature compared to where they are now. Few developers, especially ones who care about design, had much or any experience building apps for Android. A lot of early Android developers were either people with no experience at all or iOS developers who tried to apply iOS principles to Android development and failed hard. And it's possible the Android user base in general cared less about design so that in itself was not such a high priority (perhaps this is not so true now).

But aside from all that, this discussion is not really about quality per se. It is about figuring out your business idea, getting it right. Whether you then go and execute it well after that point is a different point.