You can use a passcode profile to set the auto lock settings, it's also possible that an Exchange email account setup on the device includes an organization-set restriction (like in Office 365) that prevents devices from having no screen lock.

iPod touch and iPhone will accept 5 minutes as the max value, iPad can go up to 15 minutes. Not setting a value allows a user to select "never."

Thanks for your quick respond.
That solves the problem.

Is this option still available? I can't find the  "--" symbol to choose, only time.

Excluding the auto-lock restriction should work. The "--" option is now unnecessary.

Problem:  I want to set the auto-lock to never, but no PIN code requirement.   Seems like "excluding the auto-lock restriction" requires enabling PIN code.  

Anyone else have a workaround to disable auto-lock without requiring PIN code?

@user-kqpqsmfYoB Did you ever find a work for this? I'm in the same boat.

Go to Config Profiles - search Passcode. Turn on Maximum Auto Lock (which is 15 minutes).