Switching off iPhone

You do not need a passcode to turn off your phone. Press and hold either volume button and the side button until the power-off slider appears. Then just slide to turn your phone off.

Re: “… Is there any way I can [prevent] switch[ing] off my iPhone13pro with[out] [entering] a passcode? … “

No there isn’t.

Doing so would only hinder your own ability to recover from “normal” malfunctions.

A properly functioning phone can always be turned “off” with the buttons.

Security of the device and it’s onboard data is afforded by it’s passcode.