[belorn]

Looking it up, the mrz are only there to validate that the information stored on the document is the same as the information provided by the chip, and to make any eavesdrop attacks between the reader and the chip less likely to succeed. Its an optional standard.

The data on the chip is authenticated through a country signing key. This part is mandatory and prevent the person who carries the document from falsifying the information on the chip. There is also an optional active authentication chip to prevent someone from copying a passport even if they copy of the mrz and a copy of the traffic between chip and reader.

The MRZ is also part of the older standard which is intended to be replaced by a newer system that has card access numbers, which mean that the mrz and the ascii it embeds could very well be gone from passports. This new standard was implemented in EU by 2014, so there might passports issues now without the MRZ.