Sandisk's MP3 players

Why can’t a player have both a mini USB connector plus a proprietary connector, or a proprietary connector that incorporates a mini USB connector, so the player could be connected to a mini USB or a proprietary cable?

I want the use of a AA or AAA battery so that I can carry spare batteries and not worry about running out of power, and never need to connect a player to a pc or wall outlet to charge it.  It is not to replace a rechargeable battery that no longer hold an adequate charge(that is an additional bonus).