Is there any use case (except submitting a blurred input) when you can’t do without visible SUBMIT button for a form?

I don’t want to waste limited screen space for duplicated elements, so I want to ask: can you imagine a situation when the client demands to see a visible SUBMIT/GO!/OK button that is placed somewhere near the input?

  1. If you use a physical keyboard, you probably don’t want to switch to mouse, point to a button on the screen and click it.
  2. If you use a keyboard on a touchscreen, you probably expect it to have an ENTER key for doing an implicit submission.
  3. If you use a voice to command, you expect to have a possibility to never touch any key.

If you have JS enabled, you can delegate a submit event to anything you want. But even if JS is disabled, the user must have a way to do an implicit submission without being forced to see a separate and visible button.
The only use case that I can imagine is when you want to submit a blurred input, that is, without focusing it, but in my situation, I want to disable such action. Is there another use case?

EDIT
As I said in a comment, there will be no secondary/additional functions. Just one function, especially start a search. For example, the browsers don't have such a button near the URL bar. And I'll clarify: I'm asking about a situation when the user can't do (that is, can't use a form) without an explicit, visible input...