When you reach the level 70, you'll gain the glaives. You can then go through many repetitive daily quests/dungeons/battlegrounds along with weekly Kara runs to increase the strength of your warglaives as time goes on. When BT launches, a catch-up mechanic is added which tracks all players' progress up to the level at which you've ground the entire expansion.

The Horseman's Steed was also a part of that. However, it wasn't available for Halloween, it was a very scarce release. The Horseman's Steed is my favorite since I'm not a fan the Horse with Wings models. The Legion Paladin charger is one of the only horse-like mounts that does not use the Winged Horse model (the Wind Steed is another option but may not match the aesthetics that you're hoping for)).

It's because you didn't take any action to earn them during the game. It is possible to get the top mount in the game with a credit card, or buy WOW TBC Classic Gold invest a few hundred hours of your life working towards another bird that has been recolored. Effort and reward; the stores mounts will make other mounts unworth the effort since they require so much more while you'll get much less