A hammer on a handgun gives us an extra layer of safety. If we control the hammer while holstering not only will it give us tactile feedback of what the trigger is doing, but it has mechanical advantage over the trigger. If pressure is applied to the hammer, the trigger cannot move to the rear. If something were to inadvertently press the trigger, like an untucked shirt, or the draw string on a pullover, or magic fairies bent on our demise, it (or they) wouldn’t be able to press the trigger as long as we maintained pressure on the hammer.
In the age of the striker, a hammer fired gun is almost an anomaly. While there are still a few who carry them, those people are in what I would guess to be a very small minority. There is still some appeal to a hammer fired gun, and it mostly has to do with safety.
Of the things we do with guns on a regular basis, holstering, if done incorrectly, can be one of the most dangerous. Regardless of where a gun is carried, if proper techniques are not used, the gun gets pointed at some pretty valuable pieces of meat. The extra layer of safety offered by a hammer should be a welcome addition.
Ultimately, this what I think keeps hammer fired guns around. It is also why we have things like the Striker Control Device (SCD). It offers the extra layer of safety without giving up the striker fired gun. Even though we all know that if we do it right we will never need the extra safety layers, last I checked I was still human. So is most everyone else carrying a gun. In the “human” is the word “fallible”. Trust me, it is there. Especially when you crank up the stress, or we start going faster than we should.