True. But if the mesh light mostly isn't visible, you get much more grainy renders. In addition, there are some "mesh lights" in products where you would not expect it.

I have an office scene in which two pencis, one keyboard and a metal shader do have some ambient in it. Removing that leads to a much less grainy render.

The images above are lit with mesh lights, and they have a pretty high ambient value, and that's ok. It's just that unessesary mesh lights lead to more grain and longer render times.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

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