Probably the same reason people like you dismiss all of its disadvantages.
You're rather ignoring a number of uses that gold and silver have, but that's besides the point. Intrinsic value doesn't necessarily mean the item has to have a practical purpose. It simply means that people value the item because of its own characteristics, and not because there's a law insisting that they must do so.
And yes, hard currencies have problems, and I am not someone in favor of a return to a strict gold/silver standard. But they are different problems than fiat currencies have, and IMO, problems with far less downside potential than paper currencies possess.