How, exactly, does the soft tail frame and swing arm assembly work to provide the softer ride? The rear tire of the cycle must be connected to the frame. The difference between the two frame types is the way in which this connection is made.
A soft tail frame swing arm contains a pivot joint between the rest of the frame and the rear wheel assembly which supports the wheel and the rear suspension. Also, in a soft tail, there is rear suspension, including shock absorbers which remove some of the bumps that can be so hard on the rider's back.
The soft tail swing arm attaches to the frame behind the center of gravity on the motorcycle and the pivot joint is almost always higher than the hub of the rear wheel. This provides stability and prevents 'squat' when accelerating.
Stock motorcycles are soft tails. Custom built bikes can have either type of frame and many of the highly customized cycles have hard time frames rather. For riders that really prefer the comfort of the soft tail ride, there is no reason not to fully customize a swing arm frame. Even choppers, raked and lowered with long, extended fork assemblies can be built around a swing arm frame.
So, you might ask why some people strongly prefer a soft tail frame over a rigid frame. It's really simple; it is difficult to enjoy long road trips where most of the day is spent on the pavement which is frequently less than smooth.
As more and more motorcycle enthusiasts, many of which are baby boomers, get a bit older, comfort can be a major factor. No longer are motorcycles something that only the young ride for transportation. It's not uncommon to see groups of motorcycles ridden by retirees heading to Bike Week, Biketober Fest, or another major motorcycle gathering. America is aging and therefore more riders are older and seek the comfort factor.
One major difference between soft tail frames and the hard tail frame is the way the road feels to the rider. Hardcore bikers tend to love the way the hard tail allows the feel of the road to be felt through the frame, making the rider feel almost as if they are part of the road.
Is a soft tail frame the right choice for you? That is a question only you can answer. It all boils down to your riding stamina, how much you love that sense of feeling the road through the wheels, up into the frame and into your body, and sometimes just by what motorcycle you are accustomed to riding.