You asked WHY. Simply put, because the airlines want to offer competitive alternatives. If you can move swiftly through airports, these work well.
When traveling with lots of heavy luggage (not uncommon for me) I **love** short connections. Half the time my luggage does not make it. That saves me from hauling the heavy luggage from the airport to my destination, as the airline conveniently delivers to my doorstep a day or two later. I carry on the essentials for the first couple of days.