Since the late 1960s, the Fields Medal has been popularly compared to the Nobel prize, which has no category for mathematics. In fact, the two are very different in their procedures, criteria, remuneration and much else. Notably, the Nobel is typically given to senior figures, often decades after the contribution being honoured. By contrast, Fields medallists are at an age at which, in most sciences, a promising career would just be taking off.
The Fields Medal emerged from a time of deep conflict in international mathematics that shaped the conceptions of its purpose. When it began in the 1930s, the Fields Medal had very different goals. It was rooted more in smoothing over international conflict than in celebrating outstanding scholars. In fact, early committees deliberately avoided trying to identify the best young mathematicians and sought to promote relatively unrecognized individuals.