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

Question

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...

Answer 1

Yes

The reason is, explicit design is often better than implicit design.

A submit button does more than just submit the form. It communicates to the user how the form works, and how even a micro-workflow like a single input box is supposed to work.

Assuming that a user (particularly for a consumer app) knows that Enter means submit is presumptuous design. Most users will figure this out, but it is not as communicative as having a clear submit button next to the input box.

For some forms, the button can also perform a secondary function as a call to action, because a button like Send feedback can help prompt users to act.

Answer 2

Also, it's not necessary to have one submit button for a form, though it is a norm, you can have different submit buttons that do different things, and in that case enter without the buttons wouldn't be very clear on what the intention is

^{download bmml source – Wireframes created with Balsamiq Mockups}

Answer 3

OP: For example, the browsers don't have such a button near the URL bar.

I don't agree, actually. Screen shots from four major browsers below. The way I see it, the three desktop browsers all have a huge, blue button directly below the URL bar. Now you may call this a list item and not a button, but it's a large, nearby, distinct, clickable area that the user can activate with the mouse. My guess is that it constitutes a "button" for most people.

The same is true for the iOS Safari experience - even though the button isn't coloured blue :-)

Like I wrote here, most major sites include submit buttons for their search forms, including google.com. I'm assuming they have user tested their sites and that they have made their decisions based on that data.

Chrome:

Firefox:

Edge:

iOS Safari: