Yeah, it is surpisingly limited, though I would think the reason behind this is if a older 'non-gamer' buys the machine and doens't know much about computers, they wouldn't have to worry about this whole 'memory dohicky' that lets them do SO much more with the system.
But yeah, your answer would be to just keep swaping them off and on of the SD card forwhich ones you are going to want to play, or just delete the games that you don't play as much, because you can always download them later.