At least with fixed bounty allocation we know how much "money" we get at the end. Most of them give limitation bounty participant and if you think that not worth to join you can skip whenever you want.
yes of course, when some bounty campaign using stakes based allocation people who join in early time get more reward, and this is more interest than bounty campaign based on fixed allocation even they are giving $5M or more we still get fixed allocation and not have chance to earn more money