A couple reasons:
1) To establish consistency from year to year, components of many NCs are already aged - anywhere from a year or two to [supposedly] 10-15.
2) Regardless of whether you believe noncubans are "equal" to cubans (whatever that means), their aging potential hasn't been proven as well. You could say this is a chicken-or-the-egg debate: noncuban aging hasn't been proven to help much because nobody does it, or nobody ages noncubans because it hasn't been proven to help. Whether the
came first or not, the fact of the matter is still the same. While there are books and
Encyclopaedias on Cubans and their aging potential and recommendations, nobody's considered noncuban aging that beneficial or important.
Exceptions:
Several on this board (NCRadioMan, MocoBird, Moki, RobinCoppell, others) have mentioned how much they enjoy aged Padrons. Others have found that Gurkhas, Tats, Pepins and Toranos have aging potential. Ultimately it all comes down to personal preference, but my over-riding personal opinion about aging, whether Cuban or non, is crap in=crap out, yummy in=yummier out.