Why is Zhu Yuanzhang often called the Hongwu emperor rather than Taizu?

Zhu Yuanzhang is commonly referred to as the Hongwu emperor because he adopted "Hongwu"—which translates to "Vastly Martial"—as his reign title (nianhao) upon establishing the Ming dynasty in 1368.1

While "Taizu" is his temple name and is more strictly correct in a formal historical context, the practice of using reign names became the standard convention for identifying Ming emperors. Because Ming rulers typically adopted only one reign name throughout their rule, these names became the primary way modern writers and historians refer to them, often treating the reign name as if it were a personal name for the sake of convenience.12