And not just for weddings. All sorts of pomp and ceremony would help all sorts of people remember all sorts of things. In some eras the official witnesses would be as young as possible, so they could testify, hopefully, long after, and it was not unknown to give them a good clout to ensure the event was memorable for them.
History is often difficult. Even with trained professionals, oral history gets unreliable after about 150 years. Without them, it may not last a century. Peasants, called on to testify about a deserted castle, report that it was, as far as they knew, deserted from time immemorial. This can have some interesting consequences, most conspicuously when literacy intrudes. Once in -- Africa, I think, the British took down the local genealogies. A few decades later, the locals complained that they had gotten them wrong -- the truth being that alliances had shifted, and so the old genealogies no longer supported the social structure as they had arranged it.
Though it's important not to overstate the influence of illiteracy. I was once solemnly warned in a crit that one character could only send another if they were both literate. Pshaw. As late as the end of the 19th century, there were still in some countries professional letter-writers in little stalls in the market. The illiterate would come to them to dictate their letters, or have them read. And there are many other options as long as there are literates about. Clerks for instance.