So it's only valuable because people decide it is and choose to go along with the notion that it has value
This is also entirely true of every single existing currency. The only difference is that powerful governments have beneift in there being a stable currency, and will try to keep it that way. If everybody decided the little pieces of paper and tiny bits of metal we use for money weren't worth squat, that would be true.
As for bitcoin and dogecoin: Bitcoin may eventually develop into a full-blown currency. Dogecoin was always meant as a joke. Bitcoin uses an algorithm which gets harder and harder to crack as more bitcoins are mined. Therefore, less and less 'new' bitcoins will be created, until eventually it is so slow that the value of bitcoins will stabilize. Dogecoin uses an algorithm which has a non-changing deifficulty to crack. that means that it's value is hardly able to increase at all, because it does not get any scarcer as more Dogecoins are created. Dogecoin is and will remain a joke, and only really useful on the dogecoin reddit, where you can actually tip people in Dogecoin. Nonetheless, the Dogecoin DOES have a value, and as such the Dogecoin reddit community gathered $30k in donations to get Jamaican bob sleighing team to the Olympics this year.
There are times I love that I go to college to learn about this bullshit :P.