Making a Will is not about wealth it is about making sure that what you want to happen to your estate does happen. It gives you the opportunity to specify such things as who will administer your estate, who will care for your children and who will receive specific items of your property.
Under a joint tenancy the property passes by survivorship and not through the will. This is the most common arrangement encountered amongst married couples.
On the death of one, the house becomes the sole property of the other and this is what the majority of couples would consider their wishes to be. However, there can be a situation where the surviving spouse owning the house outright is undesirable for tax reasons in particular. It is then preferable to hold the house as tenants in common.