Because it lets different organizations/organizational units control different parts of the resolution. for example, you don't want to give heroku control of your whole dns (and they don't want to be in the dns business), but you want to let heroku change the actual network ip addresses that handle your app on their own, you don't even want to have to know what it is.

cnames are what make 'the cloud' work.

Yes!

CNAME is a solution looking for a problem.

Just use A records, everything is just better that way.

Surely AAAA these days :-)