Isn't it because one of the creatures called the daddy long legs has the most potent poison in the world, just not the one we know as it?
If they really did someone surely would have died from accidentally eating one or something.
Nope its not. The crane fly isn't venomous, nor is the harvestman, and the cellar spider(the other one which is called Daddy Long Legs that actually is a spider), Wiki tells me is venomous but it's venom isn't even that effective against insects. Wiki hypotheses that with the cellar spider the myth might be born of the 'logic' one might get when seeing that cellar spiders eat the likes of the black widow, which is known to kill, so it's assumed the cellar spider has a stronger venom.
IIRC the explanation I was thinking of involved a spider that looked similar, and hung around the same habitats as the cellar spider, but was actually very venomous, I wanna say the violin spider or something like that.
Oh and if someone had eaten one, since spiders use venom, they'd be fine. Venom requires injection not consumption. Another tied in random fact .
Edited for psellign.