I do have a feeling that some "cares-about-having-silver" card is coming. The weird option on trusty steed, some comments Donald X. made in the recent secret history about cards that were scrapped, Bureaucrat, Explorer (when do you NOT want to reveal the province? Why is it "may"), and a couple other things.
Regarding Explorer: even without a "Yay Silver" card, I can think of a few odd situations where it's better for Explorer to give you Silver than Gold, mainly having to do with their different costs.
For example, say your VP is 8 less than the leader's, and your hand is Village, Explorer, Province, Forge, and a Curse. You play Village, drawing a Tactician. You play Explorer for Silver, then Forge your Tactician, Silver, and Curse into the last remaining Province, winning the game. You wouldn't have been able to do that with Gold. (I imagine there could be a simpler example involving Upgrade or Expand.)
However, even apart from that, it's important for the card to have that text for absolute clarity, so that there's no confusion for when you don't have a Province in hand; it would also take more words. (It's the same way with Reactions and a few other cards as well.)