Looking for all the reasons why devotees don't eat eggs--other than the menstrual cycle thing...Someone asked me the question below:
"I told her because an egg is like the embryo of an unborn chicken, but she said that that was not correct, and that the type of eggs that people eat would not produce baby chickens anyway."
Chicken eggs are simply unfertilized eggs, Hen chickens will lay eggs without a rooster. If those eggs were fertilized they would become embryos and would hatch. So the eggs that people eat are the unfertilized egg or flesh (yolk and albumen) or menstruation/period of a chicken. Some small farmers do sell fertilized eggs because they have roosters around, they simply get the eggs in the refrigerator soon after laying so the embryo does not develop.
So its correct an egg is not an embryo in most cases because it was never fertilized, but it is flesh and it is the result of a Hen's menstruation cycle.
And devotee's only eat what can be offered to Krishna as stated in BG 9.26
Why don't devotees eat meat that wasn't killed on their behalf? Because even if it isn't perpetuating slaughter, meat is still conducive for spiritual life, devotees shouldn't have a taste for this.
Same reason here. Eggs are a form of meat, regardless of ethics.
As such one who wants to reap the full spiritual benefits of a meatless diet should not eat eggs.
The reason devotees don't eat meat, fish and eggs is because they are unofferable to the Lord. A devotee eats only Krishna prasadam otherwise, according to Sastra, he is eating sin. So the reason devotees don't eat eggs is because Krishna will not accept eggs as an offering. Here is a quote from Prabhupada's purport to Text 26 of Chapter 9, Bhagavad-gita for further understanding:
"One who loves Krishna will give Him whatever He wants, and he avoids offering anything which is undesirable or unasked. Thus meat, fish and eggs should not be offered to Krishna. If He desired such things as offerings, He would have said so. Instead He clearly requests that a leaf, fruit, flowers and water be given to Him, and He says of this offering, "I will accept it." Therefore, we should understand that He will not accept meat, fish and eggs. Vegetables, grains, fruits, milk and water are the proper foods for human beings and are prescribed by Lord Krishna Himself. Whatever else we eat cannot be offered to Him, since He will not accept it. Thus we cannot be acting on the level of loving devotion if we offer such foods."