If I get so much traffic that scaling becomes a problem then I'll be happy as I would make a ton of money. No need to build to be able to handle the whole world at the same time, that's just a waste of money in nearly all situations.
This & sibling comments seem to imagine that every application is some special case of static web hosting, and if that is the domain you're working in I can see how you may be able to cheaply over provision to the point where you don't really worry about downtime. If you don't need distributed computing, definitely don't apply distributed computing to your problem and you'll have a cheaper and better time. I'm not some kind of cloud maximalist; if you're telling me you've done some diligence for your application and it's better off at Hetzner, sure, I believe it.
I'm pretty skeptical that this is most applications, however. Consider a browser based MMORPG where each interaction in the game will fire off one or many requests, and each player interacts several times a second. If hitting the front page results in hundreds of new players, it's easy to imagine having thousands of QPS.
Even in the MMORPG case it should be no problem at all if you get a few thousand new players(that would be some insane conversion ratio on reddit/HN traffic). Even cheap servers are fast.
However, the corollary of this is; without this responsibility, you don't have access to the great power.