I think the reason why Android has become so popular with the manufacturers is because they're free to customise the OS. If Android was just a one interface, one direction platform I don't think any of them would have taken it up.
Mobile phones are still a very competitive market and manufacturers want to differentiate their products to attract customers from another
Android became popular with manufacturers because they desperately needed to all gang behind one platform to have any hope against the incredible success of Apple. While quite a few vendors signed onto Android even before the first handsets, they did so at no cost and in name only -- the original Android army were the absolutely miserable G1 and G2 (HTC Dream and Magic), and it stayed that way for some time. At the time I was sure the platform would fail.
As Apple grew, the necessity to commit to Android grew.
Boring parables about why Android made a mistake because it isn't like iOS are as old as both operating systems, during the same time that Android has done gangbusters. My wife has a Captivate Glide with Gingerbread and Samsung's TouchWiz on it. She loves it. She doesn't know or care what ICS is, gets constant updates for the mapping and market and book reading and video viewing, etc. For the average real, non-blogging human being the model works remarkably well.
Yep, but if Google just said "Here is our OS, you may put it on your products, but you may not deviate from principles set out by us" none of them would have taken up on it.
Mobile phone hardware is generally the same across most devices these days and most of the "Joe Public" don't care what's on the inside - so the software is where the manufacturers try to differentiate themselves from each other as a selling point
Mobile phones are still a very competitive market and manufacturers want to differentiate their products to attract customers from another