A question about UMG input handling


After playing around with UMG for a bit and now reading a bit more closely into the details, I found a remark in the UE4 documentation that puzzles me a bit.

Its about the input mode for UMG widgets. it says the following about the “Set Input Mode UIOnly” node:

"…] Set Input Mode UIOnly is an edge case node and is used when you only want to allow for UI navigation only and no game input. This completely disables all game controls and UI consumes all input, use this node sparingly. "

I just wonder why this is considered to be an “edge case” :confused:
Isnt any game menu (new game, load/save/, options, etc) of this type?
Another example would be the iDroid in MGSV and similar in game management screens found in many games.

Also, why the recommendation to use this sparingly… or else??? :eek:

Anyone knows more?