Animals are my friends and I don't eat my friends.
— George Bernard Shaw (1856—1950)

Beyond animals being friends, there are many good reasons to avoid eating meat:

Animal farming is one of the main causes of planetary heating. Intensive animal farming (and the cultures needed to produce fodder and forage) contribute substantially to greenhouse emissions, promote deforestation and cause habitat degradation and loss of biodiversity.

Farming requires a massive use of land. 83% of all farm land is used to farm animals and their food, but this land produces only 18% of calories for human consumption.

The idea that humans must eat meat to live a healthy life has been dispelled by modern nutritional science, as well as by evidence from millions of individuals (including several athletes) who dropped meat. In 2018, vegetarians, vegans, and other semi-vegetarianism categories were estimated to be about 11% of the world population.

Alternatives to meat are on the rise.

The consumption of fish should also be avoided. Overfishing is the main threat to marine ecosystems. One third of all fish stocks are overfished. Destructive fishing gear, such as bottom trawling, causes appalling and lasting damage to the seafloor and its organisms. Consuming farmed fish is not a solution, because farmed fish is generally fed with wild-caught fish. Additionally, the farming of fish and crustaceans can contribute massively to environmental degradation.

Animals are not automata as claimed by René Descartes (who suggested that the bodies of animals were nothing more than complex machines). Animals certainly can suffer and, as noted by Charles Darwin, they "manifestly feel pleasure and pain, happiness and misery".

The question is not, Can they reason? nor, Can they talk? but, Can they suffer?
— Jeremy Bentham (1823) Introduction to the Principles of Morals and Legislation

The lower animals, like man, manifestly feel pleasure and pain, happiness and misery.
— Charles Darwin (1871) The Descent of Man and Selection in Relation to Sex