I can almost guarantee that over a period of years you'll see significantly less downtime that can be attributed to Heroku than you would on VMs that you manage. Even if that isn't the case, if Heroku are responsible for it then you can mostly just kick back and let them fix it, rather than spending 24 hours without sleep migrating VMs between providers.
The context here is also that of a single entrepreneur building a business. At that point in the lifecycle of a product downtime really isn't that big of a deal, customers tend to be pretty understanding so long as you recover.
Anyone who kicks back while their web hosting is down... is a psychopath. That's just not going to happen. Are you accountable to literally nobody? Even as a solopreneur, there are customers/visitors. If my site is down, I am losing money/credibility/visitors/etc. Sure, you will probably get past it, but it means preparing to communicate to those people during/after. It also means understanding what went wrong and what could be done to prevent it. Just kick back and not worry about it sounds like you're doing nothing of consequence to anyone.
The context here is also that of a single entrepreneur building a business. At that point in the lifecycle of a product downtime really isn't that big of a deal, customers tend to be pretty understanding so long as you recover.