We know from the scriptures the necessity of baptism by immersion and that Christ set the example for all to follow. We do not baptize infants or little children because, as taught in section 29 of the Doctrine and Covenants, "little children are redeemed" through Christ and "cannot sin, for power is not given unto Satan to tempt little children until they begin to become accountable before me."
But why do we baptize at the young and tender age of 8? Why not wait until they are older and, as some would argue, more competent to make such a momentous decision.
There are, perhaps, myriad reasons, but let me suggest three.