I mean, that is actually true. A restaurant that spends a lot of money on fixed costs (large tables with lots of space between them in expensive cities) will not accept a reservation for 1.
I've never heard of such a thing and from a cursory search, this could probably be considered a hidden way to discriminate and be illegal.
Just call any Michelin 3 star restaurant in an expensive city and ask for a reservation for one at a table, not the bar. It’s not at all illegal to deny this. Number of people in your dinner party is not a protected class.
That makes no sense. That's like saying a restaurant won't server a single to somebody, because they serve the best steak! Families are a good example where Dropbox are pricing themselves out (I ended up up going with pcloud because I couldn't justify paying Dropbox for all that space we don't need).