Overdrive works natively with the newer kobos (Kobo Forma, Aura ONE, Aura H2O Edition 2, Aura Edition 2, or Clara HD) you can log into overdrive on your ereader and take out the book right on the device. It's not adobe's DRM that's the issue.
Amazon doesn't make it easier to take books out the library because amazon has no interest in you doing so. They're making money by selling you ebooks, and they'd like to make it as difficult as is reasonably possible to circumvent paying them more money for content. Kobo is an underdog in the market and needs to give you a reason to buy their device and hope you buy books through them.
That's why amazon isn't interested in getting library stuff working - because there is nothing in it for them. They don't need to differentiate themselves from kobo and taking books out of the library doesn't make them any money.