1. Well, the offspring are not then locality animals -- so you've lost something of value in the breeding (i.e., the locality purity). Whether that breeding gains something else of value may or may not be the case. There are already many generic "coastals" "baja", etc. rosies out there, so this is a bit of a moot point.
2. As a matter of taxonomic fact, there are no longer any subspecies of
Lichanura. There are two species:
L. orcutti and
L. trivirgata.
(Wood, Dustin A.; Robert N. Fisher and Tod W. Reeder 2008. Novel patterns of historical isolation, dispersal, and secondary contact across Baja California in the Rosy Boa (Lichanura trivirgata). Molecular Phylogenetics and Evolution 46 (2): 484-50)
1&2. Given that taxonomy is always in flux, animals with ancestry that is mixed in any way (localities, subspecies, etc) may as a result of future taxonomic improvements be completely unidentifiable as to species (African house snakes and leopard geckos are in this situation currently). Also, the few "subspecies" crosses I've seen were absolutely butt-ugly. Seriously.
3. 'Cuz rosies are already beautiful enough.
Moralizing overview: the rosy boa sub-hobby (like that of dart frogs, and the smaller geckos) is one of the areas of the herp hobby that has not fully succumbed to morph-chasing, and many rosy enthusiasts see value in preserving that status.
P.S. I think that "Whitewater" albino has come to refer to that strain of albino, rather than simply the locality (i.e. there could be other coastal localities in a Whitewater albino and it would still be "properly" called a Whitewater albino). I don't keep albino rosies (see re: 'beautiful enough'
) so someone with more experience on this could elaborate on this point.