It’s reasonable to assume that a subset of the population thinks of these things. It is not unreasonable to assume that >50% of Gmail users have never considered it.

I didn't say anything about all or most gmail users. I specifically referred to a person who relies on gmail for his business, and who is apparently screwed without access to it. People who run businesses think through their risk exposure in general, and they get things like key man insurance policies to mitigate risks related to single points of failure. Anyone thinking through such things would realize that an email provider is a single point of failure.

Completely aside from strategic business planning, plenty of people realize that gmail doesn't provide offline access. It's obvious if you try to get into your email when you're not online. This is not the sole province of experts.

I doubt every small business manager considers ‘what’s happens if I lose my gmail’, there are plenty of trades so far detached from email where that would be the case. I doubt many plumbers are checking their business email while flying, either.