We only think it is because it's drilled into us from a young age by the educational system. But there's really no equivalent of "cheating" in real world industries where it's the results that matter. e.g. nobody cares if you took wrote the software yourself or got it from someone else's library, as long as the software product works.
If cheating happens, it is the responsibility of: 1) schools to deal with that accordingly (withhold degrees according to pre-written rules, etc) 2) employers to interview people instead of looking at credentials (something they should be doing anyway).