Logistically impossible to count only green flag laps. This isn't NASCAR where some guy gets sent off to fill two dump cans after every pitstop. Each pit has a large drum filled with alcohol fuel. There's enough in there to go 500 miles. It would be nightmarish to send the fuel truck down pit road during the race to top off almost 3 dozen fuel rigs to get to the end if they end up running an absurd number of uncounted yellow laps. The 500 woukd also become a NASCAR race where it goes on for what seems like forever. Networks probably don't like being told nobody knows how large a block of their broadcast day will be needed to run 200 green flag laps.
It's first car to complete 200 consecutive laps and it's worked that way just fine for 107 years. Leave the dumb gimmicks to NASCAR. We all have seen how well the format changes have been received by NASCAR Nation
