I would think you are probably correct. In the NBA, it is much easier to market individual players, as they are so visible as individuals. The NFL players are hidden behind pads, unis, facemasks, etc. Their only way to express individuality really is to do a dance, have a unique facemask, etc. I would guess your ideas about the owners wanting to keep leverage is probably accurate.
An interesting outcome of that however, is the star players. While a guy like Rak may be able to get local, POSSIBLY regional attention, nationally he will never be as well known as the QBs. Griff on the other hand is going to be known nationally and internationally, particularly when we start winning Super Bowls again
. IF Griff turns out to be the next marketing incarnation of Peyton Manning (big if, yes), then a VERY select few are going to have enormous amounts of power, and I'm not sure there is anything the owners can do about it.
Not sure how that all plays out, or what it means, but it's interesting nonetheless.