Why did Song Taizong let Wang Zhu serve Hanlin as a reserve talent?

Wang is good at calligraphy. According to the inquiry of Feng Qingyang's calligraphy, when Song Taizong was in power, Wang Zhu was an official in the Imperial Academy. Wang Zhu studied Wang Xizhi's calligraphy, and got the know-how of Wang Xizhi's calligraphy, so he became a reserve talent in the Hanlin Academy. Besides dealing with political affairs, Song Taizong also paid great attention to practicing calligraphy, so he attached great importance to Wang Zhu.