This is stipulated for reasons of consumer protection in the Notarization Act.
§ 17 para. 2a no. 2 sentence 2 BeurkG:
"(2a) The notary shall conduct the notarization procedure in such a way that compliance with the obligations under paragraphs 1 and 2 is ensured. In consumer contracts, the notary shall ensure that
1. the legal declarations of the consumer are made by the consumer personally or through a trusted person before the notary, and
2. the consumer receives sufficient opportunity to familiarize themselves in advance with the subject matter of the notarization; in consumer contracts subject to the notarization requirement pursuant to § 311b para. 1 sentence 1 and para. 3 of the German Civil Code, the intended text of the legal transaction shall be provided to the consumer by the notarizing notary or a notary with whom the notarizing notary has formed a joint professional practice. This shall generally take place two weeks before notarization. If this period is shortened, the reasons for this shall be recorded in the minutes.
Other official duties of the notary shall remain unaffected."