Why can't we use 什么的 ("and so on") with lists of people, and what can we use instead?
It can't be used for people because 什么的 means &quot;things like&quot;

写写信、打打球、洗洗衣服什么的 =  &quot;Things like writing letter, playing basketball, washing clothes&quot;

Also;

To list specific individuals, we can use '等人'
Example:  陈博士，李教授，王法官等人 (Dr. Chen, Professor Li, Judge Wang and others like them)

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To list different kinds of people or things, we can use '之類'
Example:
'医生，律师 和警察之類 ' (people like doctor, lawyer and police)
'足球，篮球 和网球之類' (things like football, basketball and tennis)

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'and so on' = &quot;等等&quot;
Example:
'足球，篮球, 网球等等' (football, basketball, tennis and so on)
'医生，律师, 警察等等' (doctor, lawyer, police and so on)

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To list different kinds of dishonorable people, we can use '之流'

Example: &quot;小偷, 騙子和走私客之流&quot; (the like of thief, con man and  smuggler)