How you feel about it is a personal matter, but in our society today a very significant percentage of marriages end in divorce, and most of the people who get divorced remarry. As you might expect, the majority of those who get remarried have children from previous marriages. So when people of some means enter into a second or third marriage after having had children previously, they are well aware of the fact that a premarital agreement may be in order that delineates the personal property of each party.
So we as a society readily accept the fact that people who enter into a union with their own assets and/or children from a previous marriage have a right and perhaps a responsibility to assert personal property ownership because some of their interests may not be perfectly aligned. But what about married couples who have never been divorced before? We tend to assume that a husband and wife should plan their estate together with the idea that they are like one entity that will surely agree on everything point by point.
However, even people who have been married for a long time are still individuals, and they may well have very different estate planning ideas. Rather than arguing about the matter or applying pressure until one party gives, entering into a post nuptial agreement is a course of action that can provide a solution. Once the personal property of each party has been established they are each free to draw up their own estate plan and all disagreements can be put aside for good.
Though it is the exception rather than the rule, the fact is that entering into a post nuptial agreement for estate planning purposes makes a lot of sense because we are all unique and we all have our own perspectives, pet causes and family priorities.