Among your largest assets that you plan to pass on to your children are probably your home, a life insurance policy and a retirement account. These are important assets, but their inclusion in your will may not be as important as smaller, sentimental items that do not have nearly the same financial value.
Part of the reasoning is that these large assets may pass on automatically without the need for a will. If you and your spouse own your home together, it goes to your spouse if you pass away first. If you named a beneficiary when you set up that life insurance policy, it goes straight to that person as soon as you pass away, no matter what your will says. The same is true for a retirement account with a beneficiary.
However, it's often the smaller personal items that cause your children to disagree and argue with one another. They care more about these because they have sentimental value. For instance, maybe your father gave you a watch and you plan to leave it to one of your sons. It doesn't matter that he could go out and buy another watch. That's not the same as actually having his grandfather's watch, even if he spent twice as much money. When items can't be replaced, putting them in the will is critical so that your heirs know what you wanted.
As you do your estate planning, think carefully about each aspect of that plan. Give it the attention it deserves so that things go smoothly for your family and they don't end up fighting over these items that carry fond memories.