This is actually a weasel sentence for "you are too poor" and it's kind of patronising. What do they expect to happen if solo entrepreneur get hit by a bus? That he or she has like a dead man switch that will send over all the business secrets, IP, passwords etc to a trusted person to ensure continuity?
In reality the rich look for business run by someone with generational wealth or someone who already made it and they don't trust the poor. There is an exception if they want to make a token investment, like helping the poor or disadvantaged will get them a badge in their social circle or they need it for PR.
People run their business on their own mostly because they don't have money to hire a team that will "survive" owner being hit by a bus.
So if a potential investor asks that question, it's better to politely turn them down. They are not genuine.
(I attended many seminars for angel investors, VC funds etc. and that's my take away)