Why does the Ahmadiyya Muslim Jamaat speak of the Messiah more often than of the Mahdi?

Because it is one single person who holds both offices, and because the Messiah is awaited by Jews, Christians and Muslims, whereas the Mahdi is known only to Muslims. Whoever speaks of the Messiah always includes the Mahdi.

The Mahdi, the one guided by God, is an expectation known only to Muslims. The Messiah, on the other hand, is awaited by Jews, Christians and Muslims, three of the most important groups of peoples in the world. All three link his coming with the hope of a golden age that people have always longed for.

Anyone addressing a message to the whole world will naturally use the name most people know. That is how the name Messiah came to prevail in the writings of the Ahmadiyya Muslim Jamaat when speaking of Hazrat Mirza Ghulam Ahmad (as), the Promised Messiah.

The second reason matters even more. The Messiah and the Mahdi are not two different people. It is one person with two offices. The hadith above joins the two, for the coming son of Mary is at the same time an Imam from among the Muslims. So whoever speaks of the Messiah has already included the Mahdi.

It is like a person who holds two titles. Usually the better known one is used, without the other ceasing to exist. The Mahdi remains part of the Messiah. That his name is mentioned less often changes nothing in substance.