There are a lot of applications where we want encryption to be faster. The slowness of SSL delayed its widespread adoption until _very_ recently, and is still delaying it, for instance. And ciphers are often much faster on dedicated hardware (which a good attacker will have) than in software on a general-purpose chip.
It's better to make brute-force attacks infeasible by increasing the search space than by making each individual encryption take longer.
It's better to make brute-force attacks infeasible by increasing the search space than by making each individual encryption take longer.