This probably sounds goofy, but it's an enjoyable way to keep them as well; sort of like having your very own seed catalog. I particularly like being able to flip through the pages and browse through my seeds at any given time. I couldn't do that when they were all in a box; I'd have to dump it out and the cat would have my packets strewn all over the house! Not only would he bat them around, he'd also pick them up, carry them away and hide them!
For me, the most important reason to keep them contained at all times is; a compulsion to exercise control over the possibility of having poisonous items hiding throughout the house. My cat's never been a chewer, but it only takes once!