Pushing out something completely broken that doesn't do what it's supposed to is definitely not going to work (duh!). Pushing out an app that solves the problem of managing shopping lists that has a bug where it doesn't work given a particular set of circumstances will still lead to many people using it if the users don't have any alternatives and it's better than using a piece of paper.
Software quality is important to companies because it means that they can spend more time building features instead of fighting fires, and because low quality represents a threat that a competitor could launch a better, less buggy app. Users mostly don't care so long as the app works well enough to do what they need it to do (but they're not dumb, they'll still pick the least buggy option if there are alternatives..).
A high level of quality in software is not important unless you're entering an already well-served market. I wish it was.
The cultures that tend to ship buggy software also tend to be the sort of cultures where the quality doesn't improve in response to a competitor however. But so far almost every software business has ultimately failed so being on top for a decade because you shipped some of the solution earlier works better. Customers are more than happy to buy exceptionally buggy software and games.
I wouldn't go that far. All the cases you cite are of products that definitely classify as substantially better than what they replaced.
Before Gmail took over the market from Hotmail there had been several other companies that failed due to only being slightly better.
Yes you can beat the "first mover", but doing so is hard and requires an almost revolutionizing better product.
Sure, but before that they generally make a lot more money than the second and third mover. When all is said and done, Atari and Yahoo did much better than Colecovision and Lycos.
The risk with being the first mover is that, having easily seen off competition from the second and third mover, you become complacent and stop moving.