Pre season games give veterans a chance to get their timing down for the regualar season. They probably don't require no more than two or three pre season games to accomplish this. The modern NFL players now have minicamps, OTA's and off season work outs in Green Bay. In the olden days, there were only Training camp sessions. Therefore, the modern player doesn't need as many pre season games as past NFL players.
However, 4 pre season games benefit the rookies and first year players the most. They get a chance to show their talents to the coaching staff, and perhaps make the final roster. A team like Green Bay made up of many rookies and first year players probably does not mind 4 pre season games. Especially gives the Packer inexperience offensive line, a chance to work together during a four game pre season schedule .
It is also profitable for NFL teams to have 4 pre season game schedule, because the NFL requires their members to charge regular ticket prices for pre season games and I think just about all NFL teams requires their season ticket holders to buy the pre season ticket package to get the regular season ticket package. The NFL teams pay their players a small weekly salary during training camp.
In the past , there has been talk about extending the regular NFL season to 18 games with a 2 pre season game schedule. I think the present set up in NFL. will be around for a while. The Players Union and NFL management would have to agree to any changes. That is always a problem!!