According to Ashkenazi custom, a man begins wearing a tallit (prayer shawl) after his marriage. Once a man begins wearing a tallit, he continues doing so even if he becomes divorced or widowed.

When a man marries and begins wearing a tallit, the last thing on his mind is – or at least should be – divorce. People normally plan on being happily married for a long time. Therefore, when donning the tallit for the first time after the wedding, it is naturally being done with the intention of wearing it every day from then on. In Jewish law this intention, albeit tacit, is tantamount to a "neder," or a vow; and a behavior that is the result of a vow cannot be simply discontinued.

As such, a divorced man continues to wear a tallit.

Of course, the groom has the option of stating "bli neder" ("no vow implied") when donning the tallit for the first time. But that would require extreme foresight, which in the case of marriage, might not be a great thing...