Why do some people use middle name for their first name like attorneys? And is this ok in the academic venue?
Believe it or not, there's some ambiguity in the question because of "middle name" and "use".
Example 1: I've been known as "Andreas" all my life. For the first eight years of my life, that was my middle name. My baptismal certificate says "Raphael Andreas Blass". But when I became a U.S. citizen, the idea that I'm called by my middle name didn't fit with the forms that needed to be filled out and/or with the mind-set of the official filling them out. So I became "Andreas Raphael Blass". Am I therefore using my middle name as a first name?
Example 2: Donald A. Martin, professor emeritus of math and philosophy at UCLA, writes his name just as I wrote it here on his academic publications. But everybody calls him "Tony", even in academic contexts like introducing him when he lectures at conferences. So which name is he "using"?
As long as I'm writing this answer anyway, let me give a few examples to indicate how common the use of middle names is. Just among my own past Ph.D. students, there are R. Michael Canjar and E. Todd Eisworth (about 7% of the total). Emeritus colleagues in my department include B. Alan Taylor and G. Peter Scott. Other mathematicians whose work is close enough to mine that I've cited it in my papers: C. A. R. Hoare (called "Tony"), F. William Lawvere, W. Hugh Woodin. And I'm probably forgetting a few here.