system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How running a marathon benefits a cause.

I remember as a kid sometimes we would solicit donation from family and neighbors, such as $1 per mile. However, I know many colleagues, friends, and family members who run 
marathons/half-marathons/5ks/etc... and I've never heard of them doing that. Is it mostly to raise awareness? Or are my family and friends just jerks?
gpt
Pledging.  Families/companies say that they'll donate a certain amount of money if a certain number of people run the marathon.  Plus it is generally made into a big event so the cause gets publicity.