I'm sure if you ask most merchants who accept BTC most of them are unaware how easy it is for them to accept payments directly without a payment processor and also unaware of the benefits of doing so. This is my experience anyway.
And how much more difficult is it to integrate a wallet rather than an API? In reality not a whole lot.
Why don't we focus our energy on making it easier for merchants to accept bitcoin directly rather than preaching to them to use BitPay/Coinbase?
All we need is for Coinbase/Bitpay to get hacked or run away with the coins and it's game over, most of these merchants will never touch bitcoin again. And lets not forget that fairly serious issues were found in the coinbase website during the last vulnerability bounty programme. If this keeps up it'll end badly. It's already showing signs of bad things ahead with the recent Coinbase AML requirements. Coinbase IS the PayPal of bitcoin currently and there should not be a PayPal of bitcoin as bitcoin makes PayPal obsolete.
for me, merchant acceptance happens in 3 stages
1. show them the bitpay 1% fee method, where they simply get FIAT next day in their account simply by showing a QR code. then leave them for a while to have received a couple customers and seen how easy it is to accept bitcoins
2. show them how they can use their own addresses instead and cash out elsewhere, thus saving the 1% fee, and subtly explaining that they could hoard as an investment. and mention to them a few more details about bitcoins potential
3. if they show interest in hoarding coins then simply say "well dont cash out as much then" and then go into alot more detail about bitcoin
you simply DO NOT run at a FIAT merchant full speed throwing every bitcoin benefit and detail and techno babble at them before then have ever tried it. you also do not go into your first contact with a merchant with the mindset that they will be 100% investors at the first transaction.
its called being subtle, being smart and patient.