For instance, drinking beer or wine. Alcohol is known to be carcinogenic for certain whereas with Roundup we're still talking about that tiny chance. There's always a tiny chance that a molecule from car exhaust or microparticle from a rail increases the risk of cancer, so will you say that the risk of being in a proximity of a car or a bus or a train isn't worth it?
It is important to be able to put things into context and assess the orders of magnitude. Things like beer are for certain a much bigger cancer risk than Roundup, not to mention tobacco. Still, there is much more talk about banning Roundup than beer.
Cost benefit calculations are rarely as obvious as they seem to those grieving the cost.