Don't Use Ladders

I saw an old sign on a street light which read: Don't Use Ladders, and it struck me. 

When I glimpsed it as I walked by I stopped, and went back to look again. 

It is not so incongruous a thing to see, but I have never seen one before.

It could be that the signs are old – this one looked old – and have been long removed.

Perhaps there is something, beyond my knowledge of street lighting paraphernalia, which means that this specific light cannot be scaled with a ladder. 

Possibly these signs are all over, but the discreet placement of them means I've never noticed before. 

It's a granular detail, one we don't usually see. 

What we usually see is blinkered and broad. 

Widescreen. 

Colour and shape. 

Get in close and you see Don't Use Ladders. 

Though, it is best to not know the truth of the why behind any of this. 
It is probably deeply uninteresting.