"I am genuinely asking. Why is this objectionable?"

Software engineering is at a schizophrenic point where it is very hard to categorize in either of traditional "blue collar" vocational job (given people seem to be employed close to very little formal schooling) or as a "white collar" professional job (given some roles need a CS degree level understanding of the fundamentals).

Some roles are more the other than the other.

I'd say listing a very specific tech stack signals the employer is looking for "blue collar" "commoditized" labour.

White collar "professional" types probably feel treating their contribution as "commoditized labour" is a category error.