So in most Scooby Doo episodes, Shaggy and Scooby are given the task of leading the monster to the trap. This despite the fact they are the biggest cowards. It seems to me they are tricked and/or bribed (with Scooby snacks of course).
So why are they the ones usually chosen?
A few possibilities: Scooby and Shaggy are seen as less reliable team members and so aren't trusted by the rest of the gang with the task of springing the trap. Scooby and Shaggy are legitimately terrified, so the monster will be less suspicious that he is being led into a trap. They are both pretty fast, and if the need arises, they could get away from the monster.
The main reason? Shaggy and Scooby will do ANYTHING for a Scooby-Snack. Why should the rest of the gang put themselves at risk when it is so easy to get S&S to do it?
As per my knowledge of Scooby Doo episodes, there are a few episodes where Scooby and Shaggy said they don't want to lead the monster to the trap. So they have to choose someone else, but no other member agreed. They again used Scooby snacks to bribe Scooby and Shaggy.
So to me the reasons are-
If you analyze this, then you will see there is a proper task distribution among Scooby's gang as per their skills. Daphne Blake can never be a choice because her focus is on makeup; similarly the other characters also have expertise in their own, separate work.
I think their are some exceptional episode but don't have link to them.
