Are there any known reasons why a publisher would do this and possibly confuse audiences (asking did I miss the first 12 issues of this comic?) rather than just start a new series with its own numbering?
It's a dodge publishers used to game US postal regulations. In the late 19th century there was a boom in magazine publishing. The Post Office encouraged the boom by establishing the "Second Class Mailing Privilege," which allowed publishers to mail periodicals for a much lower rate than regular First Class mail.
Comic book publishers were renowned both for their cheapness and their tendency to skirt the law. Second Class privileges let them send out subscription copies on the cheap. However mailing privileges applied only to one magazine. If a publisher had six titles he had to apply for six Second Class permits. Applying for a new permit took time and, more important for sleazy publishers, cost money. When he wanted to cancel an old book and launch a new one, instead of applying for a new second class permit as he should, Fox would use the old book's permit, insert a "formerly titled" note in the indicia, and pretend the new book was the same as the old one. Fox wasn't the only company to try this. Charlton also pulled the same stunt.
Apparently the scam worked, at least for a while. I've seen no references to the government going after Fox and his ilk for fraudulent use of Second Class privileges. Maybe the Feds didn't notice because they didn't pay attention to comics. As you noted, the scheme led to some amusing name changes. One of my favorites is
"My Private Life, formerly Murder, Incorporated."By the way, those text stories that nobody read were another nod to postal regulations. By definition a "magazine" couldn't contain just one kind of feature. Adding text stories let publishers claim their books weren't "just comics" but offered a variety of content.