We have been trying to add Nano as an option for a while now to our products, but there is no quality payment provider available that offers deposit AND withdrawals at the moment. Any company that require this (exchange, gambling etc) is basically out of luck with Nano. Any larger merchant needs both in order to handle refunds etc. to customers.
I believe this is currently holding off Nano adoption with merchants as there is no good solution out there as far as we can see. All API providers we have found are either (A) deposit only, or (B) buggy/immature solutions with which we are not comfortable with handling users' money.
I see a lot of post like "Why is Nano not used more?"; If you want to push Nano adoption as a currency used by merchant then this needs to addressed in my opinion. Any larger company will not want to set up nodes themselves but rather connect a payment API to get multiple coins in one place.