Compared to it's effectiveness against things carbon is usually used for. E.g. go look at the setup required for whole house filtration for people with actionable levels of PFAS contamination-- it ends up being like four or five 50lb carbon canisters.

If you're talking about 'safe' drinking water and want to reduce it from 2ppb to 1ppb or something-- just a 50% reduction-- then perhaps a small carbon filter is adequate.

For just drinking water RO is pretty reasonable, it's just not particularly reasonable to use RO for dishes, shower, etc. Thus the huge carbon canisters for people with acute contamination.