Because it doesn't violate the Jewish laws pertaining to food comsumption. Here they are (the common ones):
Certain animals may not be eaten at all. This restriction includes the flesh, organs, eggs and milk of the forbidden animals.
Of the animals that may be eaten, the birds and mammals must be killed in accordance with Jewish law.
All blood must be drained from the meat or broiled out of it before it is eaten.
Certain parts of permitted animals may not be eaten.
Fruits and vegetables are permitted, but must be inspected for bugs
Meat (the flesh of birds and mammals) cannot be eaten with dairy. Fish, eggs, fruits, vegetables and grains can be eaten with either meat or dairy. (According to some views, fish may not be eaten with meat).
Utensils that have come into contact with meat may not be used with dairy, and vice versa.
Utensils that have come into contact with non-kosher food may not be used with kosher food. This applies only where the contact occurred while the food was hot.
Grape products made by non-Jews may not be eaten.