The SKYWARN frequencies in their every day lives are just humble amateur radio repeaters.
As you have observed, when there is not severe weather in the area amateur radio operators like to talk about radios and otherwise shoot the breeze and enjoy their hobby.
When there IS severe weather in the area, the National Weather Service office will contact the organization responsible for the Skywarn net there (the Emergency Management office, the ARES group, RACES group, etc) and request that the SKYWARN net be activated.
This is when you will hear a Net control station come on and take checkins and reports for SKYWARN, sometimes changing the repeater into "net mode" where it acts differently.
The storm spotters for the most part are amateur radio operators that enjoy storm spotting or want to give back to their community and have taken spotter training classes (which are usually FREE and open to the public) given by the NWS. By and large they are volunteers.
You really should keep the frequencies handy (lock them out day-to-day if you must) because it is likely you will hear about severe weather there way before you will hear about it on NOAA weather radio or your broadcast media, and that extra time may just make the difference.