De nada, but bear in mind it's only ONE perspective, by one person, and I'm sure there are any number of other persons & perspectives to be found.
If these holster rigs weren't being used by somebody, for some applications, they wouldn't be selling in sufficient numbers to keep different manufacturers making them, right?
It's not like there's going to be a definitive "answer" to this sort of question, anyway.
I do tend to see them as having some practicality for those situations when a user simply can't fit a holstered pistol to either their belt, or some sort of load-bearing vest/carrier.
I was just listing some reflections regarding their practicality for everyday LE work off the top of my head ...
Sub Club #9; .40 S&W Club #1953; S&W Club #3913
Retired LE - firearms instructor/armorer