I get paid in euros and 98% of my spending is in euros.
Why would I want to use a crypto currency for payments that fluctuates with the yen, dollar, renminbi, etc?
Nobody will be making you use it - so if you find it's of no benefit, don't. As regards why there's a reason to use it when you get paid in euro, well lets go back to 2010-ish. Run a search on AAM - you will find that there was a tonne of people here scrambling for options to ensure that in the event of Ireland being dumped out of the euro, their euro would be converted into Deutsche Mark or Guilder, etc.
That time has passed but the euro project remains inherently flawed - who's to say that we won't find ourselves in similar circumstances in the future - in which case, you'd be more than happy to have funds in a currency pegged to the leading world currencies.
Other than that, it's not going to be marketed to you - it's aimed at the developing world. Not officially confirmed but its understood that FB want to trial it in India to begin with. It will be integrated with whatsapp, FB and FB messenger. That's many people's experience of the internet. It's setting itself up to be internet money in that context.
What if you're an immigrant worker in a eurozone country and you remit currency back home. A ubiquitous practice. FX and remittance services are inequitably expensive. If a FB coin achieved traction, it could make in-roads into this.
I mentioned above about the past (and potentially future) euro turmoil. That's only in the ha'penny place by comparison with the issues with currencies in developing countries. At any given time, there is a list of currencies that are being mismanaged such that you have hyper inflation. I'm pretty sure you'd be happy to hold a currency that is stabilised against the worlds top currencies in that instance.
But - is this really a crypto currency in the same sense as BitCoin. I wonder will it have a distributed ledger at all - it doesn't sound like it needs it. In some ways it sounds like a variation of M-Pesa.
Maybe I've missed something
I don't think you've missed anything. See her point no. 6 in her article. To cryptocurrency purists, a facebook coin is likely to be centralised and therefore is not their idea of a crypto. That doesn't mean to say that it doesn't have the potential to make a certain level of impact. Your M-Pesa example is relevant. Furthermore, similar moves in China towards mobile money where Wepay and Alipay have become exceptionally popular suggests there's plenty of scope in other parts of the world for a move in a similar(ish) direction.
Many proponents of decentralised crypto believe this could develop into a stepping stone towards greater bitcoin adoption.