why doesn't the us mint make more reverse proofs?

[yawnmoth]

http://catalog.usmint.gov/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&productId=14349&langId=-1
http://coins.about.com/od/coinsglossary/g/reverse_proof.htm

Thus far, it appears that reverse proofs are reserved for anniversary
dates. ie. the 20th anniversary of the gold / silver eagle or the
10th anniversary of the platinum eagle. I take it from that one ought
not expect more reverse proof coins any time soon?

[Jon Purkey]

I'm hoping the Mint will do another revers proof Silver Eagle in 2011
for the 25th anniversary. If not, I may then consider buying one of
the 2006 coins. For now, I'm happy with my two reverse proof-like
Austrailan coins. Beautiful coins.