Explain why healthy people aged 70 can’t be census enumerators

Among the 19 challenges proposed regarding the role of enumerator are questions like ‘do you enjoy knocking at doors?, ‘are you comfortable around dogs?’ and ’are you proficient at map-reading?’.
How anyone can justify the exclusion of the over-70s from the role of enumerators on the basis of these so-called challenges is incomprehensible and can only be understood as another example of exclusion through ageism.