Re:Why couldn't they use ElGammal? (Score 2)

Specs can be changed.

Indeed they can. Given the (IMHO) poor operational design of DNSSEC, they undoubtedly will be, particularly after we gain a bit of operational experience with the current DNSSEC protocol. However, the current proposed standard DNSSEC specification states that RSA is the recommended algorithm. ISC prefers to implement standards as opposed to (say) Microsoft which invents their own.

All it takes is publication of draft and going through usual process until it becomes RFC.

I gather you haven't been involved in the IETF much. It is a bit more involved than that...