Wish I'd found this post earlier before the Mod warning.
As a Georgia resident and a devoted RV'er I can tell you exactly why the system is as it is: rank stupidity.
As to the rather silly point that it makes life easier for retired folks to mosey in and out as they want, the days of "Easy Rider" are over. If you're retired and posting on this forum you have a computer, internet access and enough brain power to navigate simple programs. Make a dang reservation from the gate of the State Park the day you arrive if that works for your care-free lifestyle.
The rest of us that still have an alarm clock and obligations can't just take 'sick days' to run to a SP to find a site that fits. Corp of Engineer sites in Atlanta metro are all site specific and have occupancy rates in the 90% range all season long. Georgia State Parks have the most incompetent senior management and have been taken over by the fanatical, bunny-hugging, environmentalist crowd. The last 2 new State parks both have awful camping facilities designed by Bozo that jam pack RV'ers into very undesirable areas to probably 'lessen the impact'.
The only silver lining is that the Director has to be retiring soon and we can only get better with a replacement.