In the case of Bitcoin this is easily explained: Silk Road, "laundering" (for good or bad) and speculation. Since this is the first time many people have heard of this currency a natural question is: who is using this and why?
In the case of this specific currency, it seems like it's mainly used on social networks like Reddit for small transactions (tip), and due to its origins as a cheap joke currency it managed to get early traction. With this explanation in hand, the concrete uses becomes more clear.
Abstract values don't exist in a vacuum. There's always a concrete use of it, even if it's just speculation (Tulips) or gestures of goodwill (~ tip).
Let's say you're interested in cryptocurrencies. The hassle and expense you have to go through to get your hands on some Bitcoin is significant enough to put most people off.
By contrast, to get your hands on some Dogecoin, just post to /r/dogecoinbeg and you've got a pretty good chance of being tipped some.
Or, for people who like Bitcoin: decentralized transaction log, low/no transaction fees, and fraud protection.
Credit card companies almost unconditionally insure their customers against fraudulent transactions. Bitcoin does not. Banks will actively monitor accounts for suspicious transactions and lock the account if necessary. Bitcoin does not. Banks provide a friendly, easy to use and traceable list of your previous transactions. Bitcoin does not. Banks provide a mechanism to reverse transactions. Bitcoin does not.
As a consumer though, I much prefer the fraud protection that the credit card companies provide. And as a vendor, the 1% or less of chargebacks is probably outweighed by the number of customers who do buy because they feel safer using their credit card online.
Bitcoin/cash shifts protection from third parties, like stores, to the user. This dramatically changes the nature of security in both good and bad ways.
To swap out a word or two: "Fraud protection in the sense that, if you protect your wallet, no one can steal your cash."
I don't think that matches the commonly understood meaning of "fraud protection".
ALL
If you know someones address then you can go back and check all the transactions.
As for refunds, merchants selling using bitcoin still have to follow law of the land, in most civilised countries there is a "Supply of Goods and Services Act" or equivalent legislation where a customer is entitled to a repair, replacement or refund if the good/service is bad. Buying with bitcoin is no different to buying in cash
You obviously do not understand bitcoin or are confused about some aspects of it.
Groups of people that trust a third party can also do bitcoin denominated private transactions (the only visible transactions would be with the trusted third party). You see this at most bitcoin exchanges.
None of the things you mention are uses, they are features. Great features, sure, but it's not something that you actually do with a currency. It's like saying dollars are used by paper, or for central bank. Bitcoin - right now - is not used much for commerce, aside from black market type stuff.
This is IMO a sign that a discussion has jumped the shark and is no longer worth participating in. Once you get to the "you're either with us or against us" point people have picked their sides and you're arguing against brick walls.
In all seriousness, it's like a post-modern take on cryptocurrency. It's hilarious and thought provoking and stupid and intelligent, all at the same time. And it's so doge.
And you can actually purchase stuff with it. Cheap translation services, pictures, haikus, you name it.
I purchased 2 nonsensical stories, 1 completely useless and yet awesome doodle and a re-sizing service for a picture.
However the best part in Dogecoin is that it makes certain kind of cryptocurrency evangelists have a twitch in their eye. The amount of "Dogecoin ruins the reputation of serious cryptocurrencies!" posts makes it rather awesome.
The best quote "Dogecoin? Are you kidding me? I'm all for altcoins, but this is just making a mockery of what we're all trying so hard to turn into a respectable enterprise." This quote was actually the one that made me play around with Dogecoin a bit.
I have a hunch that this is part of the reason why dogecoin is somewhat popular. People use dogecoin because they can. And they intentionally ignore any cries on how it's not going to hold value etc. It's not supposed to. It works fine for what it already is. Tipping and nonsensical internet services.
That's a much more rational position. I mean, you'd have to be an incredible idiot to think that Dogecoin was worth something eo ipso, but slightly less of an idiot to think that there were other people who thought so, and even less of an idiot to think that other people thought that there were idiots who believed that Dogecoin was valuable, and so on.
In Doge we trust.