GAAP uses arbitrary rules for compliance which change from time to time.  They are also inconsistently enforced, regional rather than global, and essentially transitory.
In short, GAAP compliance doesn't belong in the core protocol.  It is easy enough to do at another level or with already planned BIPs that it need not be further addressed in this context.

That was essentially the answer I was given in 2005, (but without the BIP enhancements) and it still applies.