On an iPhone 8 and after the update of 13.1.2 why do you have to have a passcode? How can I delete the passcode that I put in and no longer have to have it.
Settings -> Touch ID & Passcode.
Scroll down until you see the "Turn passcode off" button. You'll need to enter your passcode first and then you can turn the passcode off.
This image is of an iPhone X with Face ID but the screen flow will be the same for your iPhone 8.
You might be prevented from performing many iOS and app functions by having this weak security. I'm sure you're already aware of these implications since you decided to not have the passcode.
Settings -> Touch ID and Passcode -> Turn Passcode Off
But be aware, this will put all of the contents on your phone at risk if an attacker manages to obtain your phone.