The appeal to tradition assumes a key part of what makes a belief or practice true or correct is its age—that is, it is old enough to be a tradition. If defenders of tradition simply went with the oldest beliefs and practices they could find, there would be no need to sort out which traditions to accept beyond discerning which are the most ancient.
But those making the appeal rarely use it to defend the ancient beliefs or practices. For example, while American defenders of “traditional” gender roles often hearken back to their perception of a past, they do not draw their traditions of sexual roles from ancient Greece. This is not surprising—though these are ancient, they are not consistent with the values that are presented as traditional by present day American conservatives. Since defenders of tradition do not follow the “oldest is best” principle, they need some other guide in selecting their traditions—some principle other than time.
This leads to the obvious dilemma: if time is the determining factor for what is best, then they would need to embrace the oldest practices and beliefs they can find. If there are other factors, then there would be no need to appeal to tradition—they could just use these other factors to defend their beliefs and practices. The first option is absurd; the second makes referring to tradition pointless—except as a fallacy or rhetorical device. While the scope of time is a problem for the defenders of tradition, there are analogous problems.
While time is obviously a factor, one also must consider geography. For example, Christian Americans who appeal to tradition when defending religious values do not embrace the traditions of the China, Persia (now Iran), or India. They focus on the United States and Europe. Not only that, they must focus on specific groups within those geographic locations—after all, there are diverse traditions in even a single American state. And even single cities. And even within a single family. Those making an appeal to tradition would need, to make a principled argument, give reasons as to why the traditions should (in addition to being from a specific time) also come from a specific location—and even a specific group. As has been argued repeatedly, if reasons can be advanced, then there is no need to appeal to tradition.
One interesting approach is to embrace a form of relativistic traditionalism: the traditions are best that are the traditions of my culture. This, obviously enough, would include a form of moral relativism: what is morally right or wrong is relative to the culture. Equally obviously it would run into the usual problems for moral relativism. One is that relativism entails that a person has no logical reason to accept the values of their culture as correct—that my culture accepts X gives me only practical reasons to follow X, such as avoiding being harmed or seeking praise. After all, if I know that relativism is true, I also know that all cultural values are equally good (or bad).
Another is that relativism ends up collapsing into subjectivism: I can form a culture of one and thus make my values the correct values—and so can everyone else. And I can change my values. This clearly collapses into nihilism—there would be no values in any meaningful sense. In the case of relativism about beliefs, there would be the usual problems for embracing relativism about truth—ones addressed at length by other philosophers, such as Plato. As such, the relativism approach would end in failure.
If an appeal is made to objective truth and objective values, then invoking tradition would be an error: there are many traditions that are inconsistent and even contradictory—so they cannot all be correct. What would be needed would be arguments to show which beliefs and practices among the traditions are correct (if any). Why, then, do people use the appeal to tradition?
One obvious reason is that it can work—fallacies often have far more persuasive power than good logic. Invoking tradition can also be seen as a rhetorical device: people often like traditions and calling something traditional can give that thing a positive feeling—though it would obviously be unearned unless reasons were given as to why it is true or good. Traditions can also often be comforting and give people a sense of stability and security—thus calling something traditional can invoke those feelings. But, once again, as a mere rhetorical device this is unearned.
In closing, I must note that I do not think that something must be bad because it is traditional—like all people, I have traditions that I like precisely because they are pleasant and comforting—but I know that appealing to tradition proves nothing.