It also cuts down on the possibility of a flood fromm filling up buckets straight from the RODI filter.

Another good thing about filtering large amounts of water at once is the quality of water you get. If you have ever noticed, the first bit of water out of the filter after it has set a while will show higher TDS then gradually drop to zero. If you just filled up a bucket every once in a while you would have that small amount of impure water in each bucket. With a big container that small amout is mixed with a much larger volume of water.
Of course that is assuming that you fill the entire container each time it gets low.