[Zikes]

We need it like we needed "use strict" in JS, which is to say not really, but it really helps. I think of AMP as "HTML Strict", a means of enforcing the rules and practices necessary for faster web sites.

[SahAssar]

So having to include another JS file to use a form or input element is best practice now?

Source: https://www.ampproject.org/docs/reference/components/amp-for...