[quote=@Sloth]"Why didn't Benji and Mary seek them out when they fell on hard times if the man felt obligated enough to seek them out in the first place?"[/quote]
As a WWI Vet during the Great Depression, especially an injured one, he'd have been struggling to feed himself let alone help other people. Benji and Mary might have known that, and wouldn't have wanted to impose on him with their own troubles.

A lot of Vets ended up setting up [url=https://en.wikipedia.org/wiki/Hooverville]shanty towns in major cities[/url], but this was improved in 1933 when the New Deal programme was rolled out by Roosevelt. The Vet could've recently come into a more secure income and deliberately come looking for Benji to help out his old friend's son, as he had promised on the man's death bed.