Dogecoin was created explicitly to have a low value suitable for micropayments & tipping. It hasn't really worked out much better for Dogecoin...interest in it seems to have waned a long time ago.

My bet is that it hasn't caught on as a medium of exchange simply because that's not really a major pain point. Cryptocurrency's competition as payment isn't $USD; it's Visa, Mastercard, Discover, Stripe, Square, and other payment processors. People bitch about these companies, but they usually bitch about them from a concentration-of-power-and-fees standpoint (which Bitcoin doesn't actually solve, once you consider the costs of the commercial Bitcoin exchanges), not a convenience one. When it comes to convenience, whipping out a wallet-sized piece of plastic or your cell phone is a lot better than waiting 12 minutes for a transaction to settle on the blockchain.