Why is it possible to have no layers selected?

[AaronDidIt]

Something I have been wondering for years - I think even a decade at this point, is why Photoshop has the ability to have no layers selected.

What function could this possibly serve? I've been working professionally with Photoshop for almost 30 years now and I can't for the life of me imagine why I would ever need to have no layer selected. 

Then there is that increbibly annoying pop-up error message whenever I try to do anything an no layer is selected as well.

Why?

If anyone has any thoughts on the purose of this can you please explain?

[TheDigitalDog]

Great question. I can't think of an answer either. 

[Rob_Cullen]

Situation: I may have an image with many layers. Many of the layers may not be visible in the Layers panel to actually see which layer/s is/are selected.

To be sure that I might only affect one (visible in panel) layer with an edit, I can De-select all layers and then confidently click on the one layer I want to affect.

Be nice if there was a Keyboard Shortcut. (I can define).

[Stephen_A_Marsh]

Be nice if there was a Keyboard Shortcut. (I can define).

By @Rob_Cullen

Save and install the following script code:

#target photoshop
app.runMenuItem(stringIDToTypeID('selectNoLayers'));

Then use Edit > Keyboard Shortcuts to assign a custom keycut to the script.

EDIT – No need for a script, it's already there:

[c.pfaffenbichler]

If people use »Show Transform Controls« for the Move Tool or View > Show > Layer Edges, yet want to evaluate the image without those elements (but with Guides) cmd-H is not useful while simply unselecting the active Layer serves the purpose. 

Then there is that increbibly annoying pop-up error message whenever I try to do anything an no layer is selected as well.

What operation could you be wanting to perform if you don’t even know which Layers (if any) are selected?