Wait for it... I can even do it on a mount. Bow before me.
In terms of "main" hub, it never was one. But it had all of the resources of one while being closer to a lot of the levelling areas on the western continent. And Alliance didn't have any capitals on the continent mainland, so on med/low pop PvP servers, it was the safer place to level. Who on the Alliance goes to 1k Needles to gank? Who goes to Feralas ever*?
Also, it was just the better hub imo. Orgrimmar was dull and Undercity was a pain to navigate. So was TB in that regard, but it was much more calm and peaceful to zone out there and get your crafting/AH stuff done. The only reason to base out of Undercity while levelling was if you were doing that late 30s chunk where you were running Scarlet Monastery back to back. But once you got whatever you wanted from the last wing, it was usually right back to Razorfen Downs, IIRC, and that sends you right back to the Barrens. Hillsbrad was a fucking war zone on my server. 24/7 Southshore v. Tarren Mill.
So, yeah. I spent tons of time in TB...and left my fair share of corpses at the base of the elevators.
*For the record, I love(d) Feralas. Dire Maul was one of my favorite instance complexes in lore and boss design that had the misfortune of being the highest pre-60 instances, so all of its gear was quickly replaced and considered sub-par...and, for Alliance, it took literally a half hour just to get to with a 5-man.