If it wasn't in Brawl, then it was probably because the extended range and power it gets when Lucario gets high damage needed to be nerfed somehow.
EDIT:Well... I'm officially annoyed... http://nintendoeverything.com/lucario-amiibo-pre-orders-sold-out-on-toys-r-us/ They're back in stock for preordering... for now.
EDIT 2: Interesting articles:
- http://www.nintendolife.com/news/2014/12/weirdness_super_smash_bros_for_wii_u_fans_find_fun_new_ways_to_brawl
- http://nintendoeverything.com/legless-peach-amiibo-sells-for-25000-on-ebay/
- http://nintendoeverything.com/sakurai-talks-duck-hunt-inclusion-in-smash-bros-8-player-smash-originally-planned-for-melee-more/
EDIT:
EDIT 2: Interesting articles:
- http://www.nintendolife.com/news/2014/12/weirdness_super_smash_bros_for_wii_u_fans_find_fun_new_ways_to_brawl
- http://nintendoeverything.com/legless-peach-amiibo-sells-for-25000-on-ebay/
- http://nintendoeverything.com/sakurai-talks-duck-hunt-inclusion-in-smash-bros-8-player-smash-originally-planned-for-melee-more/