Why are lethal dominant alleles so much more rare than lethal recessive alleles?

Lethal alleles cause the death of an organism prenatal or after the birth. Lethal alleles are usually a consequence of a mutation and they can be recessive, dominant or conditional. Since the lethal dominant alleles are harmful whether they are carried in homozygous (e. g. AA) or heterozygous (e. g. Aa) form, a strong selection against them is present and thus these alleles are much more rare.