(ל) וְאַנְשֵׁי־קֹ֖דֶשׁ תִּהְי֣וּן לִ֑י וּבָשָׂ֨ר בַּשָּׂדֶ֤ה טְרֵפָה֙ לֹ֣א תֹאכֵ֔לוּ לַכֶּ֖לֶב תַּשְׁלִכ֥וּן אֹתֽוֹ׃ (ס)
(30) You should be holy people to Me: you must not eat meat torn apart by wild animals in the field; you shall throw that meat to the dogs.
(כא) לֹ֣א תֹאכְל֣וּ כָל־נְ֠בֵלָה לַגֵּ֨ר אֲשֶׁר־בִּשְׁעָרֶ֜יךָ תִּתְּנֶ֣נָּה וַאֲכָלָ֗הּ א֤וֹ מָכֹר֙ לְנָכְרִ֔י כִּ֣י עַ֤ם קָדוֹשׁ֙ אַתָּ֔ה לַה' אֱלֹקֶ֑יךָ לֹֽא־תְבַשֵּׁ֥ל גְּדִ֖י בַּחֲלֵ֥ב אִמּֽוֹ׃ (פ)
(21) You shall not eat anything that has died a natural death; give it to the stranger in your community to eat, or you may sell it to a foreigner. For you are a people who are holy to Hashem. You shall not boil a kid {baby goat} in its mother’s milk.
Why can't Jews eat meat that has already been killed by a wild animal, or even one that died of old age? What is the significance of properly "shechting" an animal?
(1) ואנשי קדש תהיון לי "and you should be people of holiness for Me" — If you will be holy and keep yourselves separated from treif food you are Mine; if not you are not Mine.
(א) לא תאכל כל תועבה הנה קודם מתן תורה נודע הבדל בין טמא לטהור במבואר בענין נח. מכל מקום לא אסר לנח אכילתם, ואתה בהיותך קדוש, אין ראוי לך להיות ניזון מהאסור.
(1) לא תאכל כל תועבה; Before the Torah was given the difference between impure and pure animals was known as is clear from Noach (who differentiated between them in the Ark). Nevertheless it was not prohibited for non-Jews to eat non-kosher animals (as in, non-Jews did not have to keep the laws of Kashrut.) But you - the Jewish people - since you are holy, it is not fitting for you to be sustained/given life by these forbidden things.
What does holiness have to do with separating yourself from treif food? Why can't you just eat food that is healthy and good for you?
אלא מדרבנן וקרא אסמכתא בעלמא - פרש"י דרבנן גזור משום דחייש שמא יאכילנו דברים טמאים ויותר היה נראה לפרש הטעם משום חתנות.
Rashi's commentary: The rabbis decreed [that one must not eat "stewed" or cooked food of a non-Jew] because of the concern that they eat impure things. And more [than this concern] it seems that the reason [for this decree] is because of [the concern] of intermarriages [between Jews and non-Jews].
Why might the laws of kashrut be designed to create a separation between Jews and non-Jews? What does eating have to do with intermarriage?!