Ouch. I don't necessarily disagree with you. But building a scalable business is all about (and has always been about) dealing with typical users and crapping on untypical ones. I mean, look at Paypal—at least here we are talking about a fairly low-level privacy invasion to sign-up—Paypal freeze your money for being non-typical.
I agree quality might pay off longer term, but how can you provide quality to your users if you can't put food on your own table? There are always trade-offs; at the end of the day, real artists ship.
In this specific case, well, implementing a reliable registration system is a small hassle, maybe two days work to integrate and do well. I made the Siri example since there are about 6 million Scottish people and its pretty hard for them to change their accents, so it's hardly a minor issue. Ultimately everything is a hassle.
One other thing to consider, if you care about users: Facebook login is more convenient for the average user, so one way not to value your users is not to provide it. Obviously both might be better, but what other feature won't you get around to instead?
TL;DR they are doing the right thing by choosing a good, easy option for the MVP. They are accepting feature requests, so if its important and valuable, they'll do it.
(This is getting long so I should stop, but also, what's so wrong with a Facebook account? Since it has been shown they collect information on people who don't have accounts anyway I can't see any meaningful privacy loss from just getting an account).