Bitcoin at least has been used as an actual currency, with people taking it as payment and some businesses even accepting it (both online and brick-and-mortar). But I have yet to see any "Ether Accepted Here!" or "Now Accepting Dash!" signs anywhere.
I dont think you looked hard enough:
https://welovedash.com/http://spenddash.comMost shops that accept altcoins accept a variety using something like ShapeShift.io thus any coin that is on that service can be used.
Also, not yet mentioned in this thread, some alt-coins claim to (and do) offer a higher level of privacy than bitcoin