When something is permissible for benefit, it uses the language לכם (for you) or a pronoun, as in קצירכם (your harvest), etc.

And the language יעשה למלאכה does not include using for benefit.

Leviticus 11:10 says,וכל אשר אין לו סנפיר וקשקשת בימים ובנחלים מכל שרץ המים ומכל נפש החיה אשר במים שקץ הם לכם(And all that have not fins and scales in the seas, and in the rivers, of all that swarm in the waters, and of all the living creatures that are in the waters, they are a detestable thing unto you), using the word לכם for “to you”. This means that they are permissible for benefit, according to Rule 459⁶⁹¹.

Leviticus 7:24 says,וחלב נבלה וחלב טרפה יעשה לכל מלאכה ואכל לא תאכלהו(And the fat of that which dies of itself, and the fat of that which is torn of beasts, may be used for any other service; but you shall in no wise eat of it), using the wordsיעשה לכל מלאכהfor “may be used for any other service”. This does not include using for benefit, according to Rule 459⁶⁹².

footnotes: ⁶⁹¹ Malbim, HaTorah v’HaMitzvah Shemini 81. ⁶⁹² Malbim, HaTorah v’HaMitzvah Tzav 139.