Sikhi nowadays has just become an identity for most people. They feel proud they are sikh, which is good, but that's really where their sikhi ends. They drink alcohol, eat meat, practice in lust, and still call themselves a sikh. You maybe a "sikh" but not a sikh of the gurus.
There are many reasons to NOT eat meat but I will list the most important one; because our gurus said so, and it's in SGGS, over and over again. "Sikhs" who say it's okay to eat meat, even the ones keeping dari kesh, are ones who don't even read SGGS.
“You keep your fasts to please Allah, while you murder other beings for pleasure. You look after your own interests, and so not see the interests of others. What good is your word? O Qazi, the One Lord is within you, but you do not think or contemplation on Him. You do not care for others, you are mad about religion, this is why your life is wasting away.” (Kabir, Guru Granth Sahib Ji, 483)
That's what sikhi is becoming today. People are focused on the religion side than the spiritual side, what really matters.. Katha people, instead of doing actual katha are saying stuff like, "ladies should do kirtan in Harmandir Sahib" or "Stop using milk to clean the gold in Harmandir Sahib and use chemical sprays." And people listen to these guys, cuz they seem to be "modern" and just add on to their ego. I am straying a bit off topic, but this is important, we must not forget our roots. We are sikhs. And a sikh simply does what the guru says. Don't listen to these manmukhs. Read Gurbani yourself.
“Living by neglect and greed, the world eats dead carcasses. Like a goblin or a beast, they kill and eat the forbidden carcasses of meat. Control your urges, or else you will be thrown into the tortures of hell.” (Guru Arjan Dev, Guru Granth Sahib Ji, 723).