I've been on fast landings on all the airlines. I'm sure no airline would endorse or their insurance company would allow airlines to routinely make reckless landings.

I have listened in on the pilots on United and you will hear them being told to do certain things on landings, and I have heard the pilots say things like "we'll try" a certain speed and decent on flights where we have faster landings and where it feels like they are putting on the brakes a little too fast. Not being a pilot I don't know the specifics, but I am sure these factors create a smooth or not so smooth landing.

With Southwests record of safety, they must not be doing anything dangerous or it would have been documented by now. I also can't imagine in a boardroom a bunch of execs deciding to risk a multi-million dollar plane in order to shave off 5 minutes off a schedule. Sure things are pushed, but I doubt at a risk enough to endanger a plane or its passengers. Plus if it was a corporate decision you would see this on flights everywhere. I've been on some so smooth you can't even tell when the wheels have touched down, and I've been on some where you know beyond a shadow of a doubt you have landed. I'm sure there are countless number of reasons why some are smooth and some are rough.