Time is a funny thing. You spend hours yanking the handle to produce good quality ammos, but don't want to take a relative fraction of that time to organize it?
I've started using ammo cans for my bulk 9mm and 223, which I load several thousand rounds at a time in my Dillon. For everything else I don't load at enough of a volume to really care about taking the time to box it up. And to be honest, it's less about the time it takes, as it is about the added expense of dozens of extra ammo boxes.
That's kind of where I'm at. The majority of my handgun rounds go in 50rd boxes, but some, like my 9mm, just go into bigger plastic or cardboard boxes... I'm just going to dump it out on the tailgate or bench to load it into mags, anyway. Rifle ammo is a little different, because of what I shoot. I store some of my rifle range ammo in cardboard boxes, about 100-200rds each... it takes up much less space than the plastic boxes, and is largely unnecessary, but other rifle ammos get put in 50rd plastic boxes, or 100rd MTM boxes. Much of this is because of how I store my loaded ammos... limited space requires me to have it organized, and my OCD requires me to have it in like sized boxes or containers, not random bags or old coffee tubs, so I can keep track of quantities.
Recently, however, I have fallen in love with the small plastic 'ammo cans' available from MTM and the like, smaller, even, than the MTM's in KC's photo above, and a little smaller than a .30cal GI can. Those seem to be the Right Size for some bulk ammo, and aren't too heavy when loaded to capacity... because I don't inherently trust plastic boxes or latches. I have 1 as my range tool box, and 2 as bug out cans, loaded with ammo and magazines as appropriate.