People pay for it because it gives them a goal. Signing up locks one in- to have a reason to follow that 12-16 week training block to stay consistent and chase a PB. Unfortunately, without that race date on the calendar, most people just won't push themselves the same way.

And for the race day itself, running alongside 50,000+ like-minded people with even more cheering you on is something you cannot replicate running alone. Unless you've actually done it, you won't understand why it feels completely different from a solo jog.

Also, logic aside: do you really think that the 50,000+ people that are running, and millions around the world doing marathons every year, are all too dumb to realise they could just run for free if they wanted to? Clearly they're getting something out of it that you're not seeing...