One nice feature of Suica Apple Pay is that once set up it’s just a regular Suica transit card. You can recharge Suica Apple Pay with cash, and you can use it without a network connection: Suica Apple Pay works just fine with Airplane Mode on.
This is handy for long train trips when you want to conserve battery power. The one thing you don’t want to do is run out of battery power before going through the ticket gate of your final station. With Airplane Mode on you’ll have plenty of juice for your entire trip and can still use Apple Pay.