Pourquoi? Probably because of the nasty-cute Pathfinder goblins and the current buzz about them.
Remember that the worgs are not dumb animals. They are bigger, stronger, faster, and tougher than the goblins. They are allies, not slaves - the only reason they tolerate the gobbos at all is because goblins have hands. Gobbos can make ranged attacks. Gobbos can scavenge armor from dead humans - too big for a goblin to wear, but with a little cutting and lacing it can make decent barding for a worg. Worgs are much better at (literally) sniffing out traps - but goblins are better at disarming the trap once found.
In close combat, a goblin worgrider should probably use Aid Another to improve his worg's attack - he's automatically adjacent to both the worg and the worg's target, his chance of success is much better than trying to hit an armored opponent, and the worg's bite does a lot more damage than the rider's pitiful weapon. Consider a house rule allowing worgs to advance by class rather than HD - even a single level of ranger (favored enemy:humans) or bard (your howling buffs the whole pack) significantly improves a worg's threat level. Scout or rogue levels fit the instinctive flank-slash-and-run tactics of a wolfpack. Maybe it's the Wolf Queen the PCs should fear, rather than the Goblin King...