Why religions don't allow to eat beef ang pork?

The Hindu brahmins do not eat any meat or eggs.

Many Buddhists don't eat meat. At a Buddhist event or retreat the food is almost always vegetarian, sometimes vegan. Most Buddhist nuns and monks are vegetarians.

Some Buddhist traditions, such as in Vietnam, do not eat meat on the day of the full moon and the new moon. This is a good habit to try.

The main reason is not wanting to cause suffering to animals. Nowadays it is also an ethical decision based on the fact that it takes so much more of the world's resources to create a pound of meat. It takes land, grain, petrol/gas and lots of water, much much more than to produce a pound of rice, wheat, vegetable, etc. In Buddhist terms, by being vegetarian we are being compassionate to the earth and our fellow humans by not using up more of the earth's resources than we truly need.