This house ad got me thinking a wee bit:
But it does play up the "we're all the same company" aspect--having Mr. Justice and Steel Sterling and Black Hood interacting with Archie and Jughead--in a way you don't see anymore.
Through the Silver Age, you would regularly have house ad touting a company's different type of fares. Just look at Bully's 365 Days Of DC House Ads, and you'll see DC's super-hero books regularly included promos for Sugar & Spike, the Maniaks, Jerry Lewis, and all sorts of variety. Even Marvel, with a much smaller output than DC at the time, would have ads encouraging you to check out Millie The Model or Not Brand Echh.
I suppose part of it is that, despite the number of titles published today, there is a much smaller variety of comics published, especially by the big two. Despite an arbitrary commitment to publish 52 titles per month, DC has gradually phased out anything that wasn't a contemporary super-hero comic--no room for teen hijinks or talking babies or anything that isn't Batman or Superman or Justice League related (even All-Star Western is now a "cowboy trapped in the 20th century" book, at least for the rest of this year). Ditto Marvel.
And of course, as the jokes about The Punisher Meets Archie attest, it might be inappropriate, in these days of "mature" comics, to be advertising kiddie far, even if the companies had any. "Hey, kids, the Joker just cut his face off--now go read Sugar 'n' Spike!" would be pretty terrible and controversial advertising strategy (so much so that I'm surprised that clueless DC hasn't already done it...).
And that's all I have to say today.
Ad is from some damn MLJ comic I forgot to right down--probably an issue of The Hangman from the mid 40s. Deal with it.