The point of a signature on paper is that (at least in my country) you can summon somebody in court and ask "is this your signature"? If they say it is, it is, even if it does not look much like any of their other signatures. Then there might be a suspect of false testimony or being blackmailed etc but that's not always the most important issue in a case. E.g.: if it is a contract and all the signers state that they agree with its terms, then there is no much else to discuss.
