If local custom weren’t a factor, then a significant portion of Ashkenazim wouldn’t wait only 3 hours and an old Sephardic community wouldn’t wait only 72 minutes.
Minhag is a function of context and geography as much as it is a function of text.
And for the record, I wait 72 minutes, which is the practice of the Sephardic Jews of the Spanish and Portuguese minhag, which is the original Sephardic way.