What is the reason for wearing tefilin?
is it to induce a person to study torah? Or perhaps in order to remember the exodus from Egypt?
If so, what is the connection between this to wearing black leather boxes with straps hanging down?
The physical properties of the tefillin are distinctly not described in the Torah. This fact is sometimes used to discuss the validity and usefulness of oral tradition.
This source sums it up pretty nicely:
There are also a few discussions on this topic at chabad.org. Including this on the types of hide that may be used for the parchment:
The reason for tefillin looking the way they do is because G-d described them to Moses on Mt. Sinai.
The reason for wearing t'fillin comes from the first paragraph of the Shema
And also from the second paragraph of the Shema
The gemarra Sanhedrin 88b and in other places discusses the form of Tefillin, explaining what the Torah means when it says to tie them to your hand and between your eyes.