Most people running marathons are rcreational and tempo keeps the overall volumes far lower and safer. Much of the damage I’ve seen with marathon runs occurs over the last few weeks of training where long preparatory runs are done.
We’ve had several clients who wanted to do the marathon (don’t ask me why) and so we just trained them as normal and they did the run. One girl had trained with her boyfriend for several months but he switched to traditional training a month out and she just stayed with tempo. On race day she went out together with him but left him over the second half and could have run faster, she felt, if she had left him earlier in the race.
Same for a 50 yr old who trained with us. He had a group of business associates who wanted to do it, so he agreed but stayed with his normal training, and beat them all anyway, leaving the rest of the group pretty pissed off.
Many who do the traditional final prep period become so blown out after the marathon itself that they have to stop training for months to recover.