Sforno on Deuteronomy 14:21/ספורנו על דברים י״ד:כ״א

1לא תאכלו כל נבלה, even of the pure species which you may eat after they have been slaughtered ritually.

2כי עם קדוש אתה לה' אלוקיך, even though the dead carcass is in a state of being fit for human consumption, such as by strangers in your midst or residents who have not yet converted to embrace all of Judaism’s laws. עם קדוש, ready to achieve the perfection intended for it by its Creator. (this would be slowed down or impeded by eating lower forms of living creatures, not that eating them would be harmful, objectively speaking.)

3לא תבשל גדי, as is the custom among the Gentiles who believe that by doing so they will increase the numbers of their livestock (compare Moreh Nevuchim, section three 3,48)