Just because it's not consistent doesn't mean that it's not important. I fail to see how getting hits with runners on 2nd and/or 3rd isn't important.
A stat like RISP, that provides an extremely small sample size, and has been proven over time to correspond to the player's other statistics, doesn't actually matter. No decisions should be made based off this number. Therefore, it should theoretically not matter at all to anyone.
However, it's actually a good thing to know, and something that fantasy owners who need a 1B should look at. Morneau should start to see himself pick up more RBI over the coming months
. So in that sense it does matter, because people who do not look at the RISP could sell you Morneau at a nice price...