Why is DSA falling out of favor?
One disadvantage of DSA as conventionally implemented is that the key can be compromised if signatures are created on machines with poor random number generators.

In the wake of the Debian openssl fiasco this meant that any DSA key that had been used in an openssh client on an affected machine was potentially compromised. With RSA keys only keys generated on machines with the bad random number generator were affected (and were dealt with by a blacklist).