I do agree that it would not make sense that Kashrut is intended for health benefits. I think it is good that in many cases Kashrut has led to more healthy eating. I am glad it is not Kosher to eat bugs and creeping things as I am sure they probrobly carry a lot of germs. But it is said that Kashrut is very, very important to the divine soul.
Here is some Chochma concerning Kashrut
Whosoever eats forbidden foods…
1) Is judged as a despised person since Hashem loathes him in this world and the world to come. (Zohar-part III, 41.)
2) Defiles his soul (ibid) (Reishis Chochma)
3) Will suffer much since all of a man's suffering in this world is because he was not scrupulous in the observance of kashrut. (ibid, 42)
4) Attaches his soul to the forces of impurity and a spirit of defilement rests upon him. (Ibid)
5) Leaves the sphere of holiness and enters a sphere of impurity. (ibid, 42)
6) Woe unto him and woe unto his soul. He has not attached himself to those of the eternal life. (ibid, 41)
IT IS AS IF HE WORSHIPS IDOLS
7) Is as though he has a worshipped idols G-d forbid. (ibid,)
8) Has no part of the G-d of Israel (ibid, 41)
9) Will have his face take on the appearance of a wild animal. (Zohar part II, 125)
10) Is as though his soul has left him and he remains a living corpse and is considered evil. (Chasam Sofer Parshas Shmini)
11) Has entered within him thoughts of atheism and heresy. (Rambam)
12) Unintentionally defiles his soul; with intent – his soul becomes like that of a lizard. (Or Hachayim Shmini)
HE PROLONGS THE EXILE
13) Prolongs the coming of the Mashiach, (Bris Mateh Moshe)
14) Does not belong to Hashem (Rashi on the verse A Holy Nation")
15) Forces his soul to become subservient to the body and its physical environs. (Sefas Emes, Parshes Shmini) 36) even though he merely is lenient in something which requires stringency, defiles his soul and is unable to comprehend the ideas of the Torah. (Meor Veshemesh)
16) Will see his children turn to evil ways. (Igre D pirke 126)
HE WILL COMMIT OTHER SEVERE SINS
17) Will commit other severe sins and will fall prey to the evils of the gentile world. (Divrei Yoel Parshas Shmini).
18) Even rabinically forbidden foods, brings one to further sins (Kav Hayashor, Avot D'rabeinu Noson chap. 15)
19) Creates an impurity in his heart and soul (Mesilat Yesharim)
20) Feeds his body with prohibited objects. Eventually his body will become filled with all types of impurity. (Nidchai Israel chap. 29)
21) Will have impurity become another limb on his body. (Reishis Chochmo Shar Hakedusho chap. 17)
HE CAN NEVER BE PURIFIED AND DESTROYS HIS SHARE IN THE WORLD TO COME
22) Can never be purified and destroys his share of this world and the world to come. (Yesh S'char pg. 42)
23) Because of minimal impurity one can be brought to the depths of Gehinomm. (Arugath Habosem)
24) Most apikorsim (heretics) have become so due to eating neveilos and treifos. (Chasam Sofer Kdoshim)
25) Because of unsuitable shochtim, Jews are unable to earn a livelihood. (Likutei Moharan)
ENTIRE JEWISH COMMUNITIES HAVE BEEN LOST THROUGH THIS SIN
26) There is no sin so severe as forbidden foods, since entire Jewish communities were lost and turned to evil ways because of eating treifos and neveilos. (Divrei Chayim-Yoreh Deah)
27) Will find it impossible to pray with the proper devotion and intention (Or Haganuz - Parshas Toldos)
THOSE WHO STUMBLE THROUGH FORBIDDEN FOODS BECOME INSOLENT PEOPLE AND ARE THOSE WHO DON’T FEAR G-D
28) The majority of insolent people in every generation, failing in yiras shomayim (fear of Hashem) and non-acceptance of rebuke come about by eating forbidden foods. (Pri Chadash -Yoreh Deah 81)
29) Will become a heretic and evil. (Shulchan hatohor quoting the Ari z.l)
30) Is held captive by his own impurity and is thus unable to ascend to holiness. He is unable to separate himself from his impurity until he is buried in the grave or through consistent penitence and fasting. (Sefer Tfila Lemoshe, chap. 68)
31) Even unknowingly, needs to repent for the wrong he has done. (Sifrei Chasidim in the name of the holy Baal Shem Tov)
The whole matter of death in this world came about because of the sin of eating something that was forbidden, the fruit of the Tree of Knowledge As it is written (Bereshit 2:17): “But of the tree of the knowledge of good and evil, you shall not eat of it; for in the day that you eat of it you shall surely die”. As a direct result of it, death was brought onto the world to all men for all generations.
The Ramban