If you can produce a quality ePub file, and you don't have any particular interest in Kindle Select (which requires exclusivity), I see little reason to limit yourself to Kindle.
Why limit yourself to only Kindle readers? There's a big world of readers out there. Get your book in front of as many of them as you can.
Of course, using multiple retailers does create more work for you. You will need an account for each. The biggest nuisance is setting up your payment and tax details--each retailer has their own peculiar ways of doing that. But you have to do this work only once per retailer. A nuisance, but a one-time nuisance.
And using multiple retailers multiplies the amount of work per book. Now have to describe the book and upload the cover and ePub files once per retailer. It also multiplies the amount of effort to make changes (e.g. new cover, update to fix typos, update front- and back-matter, and so on).
Aggregators like Smashwords and Draft2Digital can greatly reduce the amount of work you have to do. You upload your files to them, and they distribute to the retailers (including Kindle, iBooks, and many, many others). The tradeoff: They take a cut of each sale.
I currently go direct to KDP, and use Smashwords and Draft2Digital to distribute my books to other retailers. Some day soon I may go back to working directly with the major retailers (iBooks, Nook, Kobo, a few others). But for now I'm (reasonably) happy to have Smashwords and Draft2Digital do the nuisance distribution work for me.