[Burgers]

You do know that Frontier was purchased by a private equity firm right? Indigo Partners stated in 2014 that their goal was to transform Frontier to a ULCC so its no surprise they ditched the free bags. I highly doubt a private equity firm wants to own an airline longer that it absolutely must so its pumping up the balance sheet with ancillary fees.
People that fly Frontier are very price sensitive (polite way of saying cheapskates) as long as they keep their prices a couple dollars lower than their competitors they'll win the business.
Alternative airports with lower costs is often part of the ULCC strategy so no surprise they use TTN vs PHL.