Is there a reason why the reward for mining, currently 25 coins per 10 minutes, halves every 4 years, instead of decreasing smoothly?

Every   ((4 years) * (365.25 days/year) * (24 hours/day) * (6 payouts/hour)) = (210,384 payouts), the payout halves. Instead, the payout could be reduced by a factor of (the 1/210384th root of 1/2) = 0.99999670532911859551036168842216 every 10 minutes.

In this way, there would not be a huge jolt to the mining system every four years. Granted, the system survived its first jolt, but why have such a stress in the first place?