Add to that the declining experience of email with so much marketing and trash landing in the inbox (and sometimes Gmail categorizing important emails as "Updates")
That's why grace periods for these situations are important.
Who uses SMS? This might be a cultural difference, but in Europe they are still used a lot. And would you be ok if your utility company cut your electricity bill just with an email warning? Or being asked to appear to court by email?
This is also something under your control - you don't have to use Gmail as your email provider for important accounts and you can whitelist the domains of those service providers if you don't rely on a subpar email service.
That period should definitely be longer than a few days.
Hetzner is great for cheap personal sites but I would never use them for any serious business use-cases. Other than failed payments, Hetzner also has very strict content policies and they use user reports to find offenders. This means that if just a few users report your website, everything is deleted and you're banned with zero warning or support, whether the reports are actually true or not. (This also means you can never use Hetzner for anything that has user uploaded content, it doesn't matter if you actively remove offending material because if it ever reaches their servers you're already SOL.)
But if you do not pay and you do not check your e-mails, it's basically your fault. Who is using SMS these days even?