The answer to the 'why not?' Isn't that simple but really, it could be. If you had, say, 6 retainers, you would amass venture items 3X the speed of everyone with only two. Not to mention the extreme benefits of having 120 items for sale would give you. That list would push this game closer to the Pay to Win strategy of game. Which isn't fun for the long haul. But limited retainers would be fine. Just space to put more stuff. I had to buy the 2 extras 2 weeks into playing. By week 6 they were full. Im constantly juggling items into and out of my own inventory, which usually is full all but for about 6 spaces.