There will always be a few specimens that either flunk the aptitudes than go on to be sky gods or ace the aptitudes but can't wipe their own @rse. However, this is not the norm and I'm sure that if you examine the trend over the years it implies that generally the ones who achieve a better aptitude score are less likely to fail flying trg at some point. With the lack of funds today, you need the best possible indication that someone who starts training will finish to the required standrad.
As has been discussed many times before, essentially you can teach anyone to fly; given enough time. BUT Less funds = less time = more risk of getting chopped, thus entry standrads MUST be raised.
It can't possibly make sense to do it any other way.