People often overlook one very important matter in the excitement of a wedding: any pre-existing will (unless it is stated to have been made in contemplation of the marriage) will become invalid. This in turn means that it is likely your new spouse will inherit your estate regardless of what your prior will provided.
This might not worry young people who are marrying for the first time and do not have children. However, consider people who have children from a first marriage/relationship and are entering into a subsequent marriage. The effect will be that the new spouse inherits and the children miss out.
If you do not intend for your new spouse to inherit your entire estate it is crucial that you update your will in contemplation of or as a consequence of your marriage. While your children will have the right to challenge this situation should you die it is far easier to adequately provide for them in the first place.
Similarly, a divorce will also affect your will in that it will revoke any appointment of a former spouse as executor, trustee or guardian. Gifts to the former spouse will also be revoked. You may be thinking that’s fine, I wouldn’t want them to benefit anyway. In reality there is often a considerable period of time between a separation occurring and divorce actually taking place. In many instances people never get around to actually getting divorced so their will remains valid.