How come there’s no standard way to submit a web form with the keyboard?

I know that in general you can hit Enter while focused on a form field to submit a form. However certain elements like selects and textareas break this behavior. How come we don't have a web standard that permits the user to submit a form with the keyboard regardless of the type of element that's currently focused? (tabbing to the Submit button is not a reasonable general solution, it takes too much attention and time)

Incidentally, I noticed some sites (e.g. Asana, Gmail, GitHub) introduced Ctrl-Enter to reliably submit with the keyboard. Is there any effort to standardize this behavior in browsers through an RFC? This seems like a glaring hole in web forms.