Why? To understand and evaluate medical and scientific research, and apply statistical knowledge to clinical practice with clarity.
But mainly, out of curiosity.
"Self-education is, I firmly believe, the only kind of education there is." Isaac Asimov
"I always try to be aesthetically right." Gilbert Strang
"When I was student, I always went to his [Gerd Faltings'] lectures, and never understood anything. But I must say that, looking back at this, I learned so much from these lectures." Peter Scholze
"The mathematicians estimate money in proportion to its quantity, and men of good sense in proportion to the usage that they may make of it." Gabriel Cramer
"Si de algo soy rico es de perplejidades y no de certezas." Jorge Luis Borges