Mandatory TLS is coming
Well, not exactly mandatory but Chrome will start labeling any text or email form field on a non-TLS page as “NOT SECURE”.
Chrome 62 will be released as stable some time around October 24th. If you want to avoid the customer support overhead then, regardless of whether any of the information on a form is sensitive, you should probably make sure that all your forms are accessible via TLS and redirect any attempt to access them over plain http to https. You can do that globally for a whole site pretty easily, and there’s not really any downside to doing so.
I still have half a dozen sites I need to convert to supporting TLS – the cobbler’s children have no shoes – and I’m beginning to feel a little urgency about it.