It prevents the use of marked cards and ensures that decks are uniform, reducing the likelihood of cheating
As a landfall-focused commander, it thrives in green shells that want to keep dropping lands while rewarding you with high-voltage damage each turn
Kuldotha Red and various Boros builds get enough tokens going around that playing this, ditching a small 1/1, and blowing up a Myr Enforcer or a land seems like a pretty good tradeoff
In order to outscale the powerful lategames of other decks, UB relies on triggered abilities which add free value to every turn
Worldsouls Rage Worldsoul's Rage pulls double duty in ramp decks
The real boon Hostage Taker provides, however, is Magic 's version of Stockholm syndrome as you can cast the exiled card as long as it remains exiled, and you can spend mana as if it were any color to cast it