Infertility treatments always aim to imitate the natural process of conception as much as possible as the first option. With conventional IVF, the sperm reaches and penetrates the egg by itself. However, in IVF with ICSI procedures, the embryologists injects the sperm directly into the egg. This is the reason why conventional IVF is more similar to natural conception.
Also, the sperm is chosen by natural selection, while with ICSI it is done following the criterion of the specialist. A sperm capable of fertilizing the egg with their own power is a healthy one, and therefore one able to create viable embryos.