I don't think Dogecoin really has a price to use, but it has existed relatively early and is still alive. Over time, as new investors join in, they will hardly pay attention to this altcoin.
Dogecoin is one of the best alternative coin that's serving the purpose of what other altcoins are trying to market for themselves. Dogecoin has a better use than those altcoins that you may now, being cheap with its fee and reliability of its speed is what making people like dogecoin.
Until now, we have no idea why it's not on Bitfinex but I guess Dogecoin doesn't need them and it's listed in almost every popular exchange.
yeah . dogecoin is always available every popular exchange today so we shouldnt worry if one exchange dont list it . dogecoin is a good coin tho and many people use this due to the reasons which you already stated above but there are few that hates this coin and make joke of this coins there are even people call doge coin a joke coin . this is what i believe when i hear the name doge coin before but it all change until i started using this coin . we dont know maybe bitfinex is one of those doge coin hater and they didnt ever try to use dogecoin before they judge it .