Multi-table no-limit hold'em tournaments differ from cash games in several respects, a key one being the increase in blinds and antes that constantly affect the significance of chips, making stacks "shallower" (relatively speaking) and forcing players into action. The way most tournaments pay out — with only the top 10 to 15 percent (sometimes more) getting a piece of the prize pool and the biggest cashes up top — also makes tournament poker very different from cash games where every chip has an assigned cash value that never changes.
In other words,in tournaments the value of chips is constantly changing.