During the Roman occupation, the Empire needed a way to fund its expansions and general upkeep. To gather funds, the Romans would enlist the help of locals to gather taxes in exchange for a cut of the profits.
In the eyes of the average Israelite, tax collectors were traitors to their culture and beliefs. Having one of the apostles be in that category would be like advertising that one of your corporate leaders was a former child trafficker on the company website.
To put it kindly, it wouldn’t make for good public relations if you made up something like that.