They lost all meaning the moment the brand split happened. Wrestling used to have a world champion who was without a doubt the number one or two(if he was a heel) guy in the company. They used to hold the belt for a year, or at least 7 or 8 months at a time. With world titles locked up and only changing hands at a ppv, it gave the midcard guys a secondary title to fight for. The IC champions of the past where bigger stars than most world title holders today. Perfect, Bret, Owen, Bulldog, Ramon, HBK, Triple H, Steamboat, Savage, Piper, and Honky Tonk were all huge superstars that defended the IC title for months at a time. It changed hands more often than a world title, but not by much.
When the brand split happened, we now had two world champions. If neither world title is recognized as being the most important in the world, how the hell would people care about a midcard belt. Since the Smackdown champion is usually a smaller star than the Raw champion, the Smackdown belt is basically the new IC belt. With one world title Eddie, Benoit, Mysterio, Christian, Sheamus, RVD, CM Punk, Swagger, Khali, Booker T, Jeff Hardy, JBL, and maybe Edge would never of been a world champ. The Smackdown world title has become the new IC/US belt. The IC/US titles are now more like the old Hardcore and European championships that got thrown around just to give a guy a push.