Counterpoint: I lost a domain when a registrar went out of business, and another when a registrar bumped the price 10x and refused to give me authenticode unless I physically show up to their office. Sure, I cheapened out and used shady cheap registrars, and this all happened a while ago so things are probably more regulated now, but for comparison I never permanently lost access to hosted email. (Losing access tempo…
On the one hand, using national TLDs can be a problem if the area you live in is no longer considered part of your country (I imagine .ua owners may have that problem in the future with the way things are going). On the other hand, using TLDs like .com/.net/.ai/.io puts your domain under control of foreign law enforcement (US for .com/.net, UK for .ai/.io).