I can’t speak for everyone but when it comes to online orders at companies that I either rarely (or never have) order(ed) from, I will always choose the Apple Pay option over ‘continuing as a guest’ or ‘making an account’ (or PayPal for that matter, since its more complicated than Apple Pay). Don’t discount ease of use: pulling out my phone and letting faceID run is way better than having to type all my info in (not to mention more secure)
If Visa/Mastercard can force businesses that accept their cards to include the ability to use this payment method that might be a competitive advantage over Apple/Google Pay. Not sure they would have that leverage, though. We have seen what kind of ridiculous shenanigans a place like Walmart will get into to avoid making it easy on their customers if it means losing control of even the slightest amount of customer data.