This has been marked by Kory Kramer as a Duplicate of Add Ability to lock a map frame on a layout to prevent zooming. Please visit that idea to up vote and add uses cases in the comments.
I'd like to be able to access the Identify Tool while in the Layout mode.
I'd like to be able to activate the map I want to be active in the TOC (similar to ArcMap), and then set the Explore button such that I can identify in the same manner as when I've activated the map from within layout mode.
The advantage here is I can identify features while zooming in on the layout and not the map thereby maintaining my set extent in the layout.
In real-life this is especially handy when management is "watching over your shoulder" and asking about a particular feature. Keeping the map set to the layout they are used to seeing is extremely useful because it prevents them from asking additional questions about new features they may see as you zoom in on the map view, (which changes your map zoom). Zooming on the layout means that the stuff on screen is the same stuff they see on their paper map in their office and helps them, (and I), focus on their question without invoking new questions.
I used to zoom in and identify things while in Layout in ArcMap and I'd like the same functionality (with the improved identify features), in Pro.