I absolutely agree that in the long term they’re a much better option. But my drag-around gas generator cost 500 bucks, while my solar system was $22k and I got quoted $18k for a single battery.
If we're talking long-term, the generator will easily outlast the solar panel and/or battery if you maintain it properly (which is honestly very trivial as upkeep goes).
He already has a battery, a Honda EU2200i to supplement it during blackouts would only be $1,200. Outrageously cheap compared to installing a 2nd home battery.