Realistically, the target audience are organizations as nowadays most business laptops are being carried between docking stations with the occasional meeting or air travel in-between and 13" is an excellent size to meet those needs.
When hooked to a docking station, the screen size and keyboard is entirely irrelevant and modern laptop performance is…honestly crazy good.
When in a meeting, it’s probably being either used to take notes fullscreen or show a presentation, so pretty neutral.
Finally, when traveling, you can really can feel the difference between a 13" and a 15" when you’re running on too short of a layover between flights.