doc: few words on wy this library exists

docs/index.rst

@@ -1,11 +1,11 @@
 The `datasalad` documentation
 =============================
 
-This is a pure-Python library with a collection of utilities for working with
-data in the vicinity of Git and git-annex.  While this is a foundational
-library from and for the `DataLad project <https://datalad.org>`__, its
-implementations are standalone, and are meant to be equally well usable outside
-the DataLad system.
+``datasalad`` is a pure-Python library with a collection of utilities for
+working with data in the vicinity of Git and git-annex.  While this is a
+foundational library from and for the `DataLad project
+<https://datalad.org>`__, its implementations are standalone, and are meant to
+be equally well usable outside the DataLad system.
 
 A focus of this library is efficient communication with subprocesses, such as
 Git or git-annex commands, which read and produce data in some format. The
@@ -30,10 +30,11 @@ shell command, while reading its output back as a Python iterable.
     b'three'
 
 
-
 Package overview
 ----------------
 
+Also see the :ref:`modindex`.
+
 .. currentmodule:: datasalad
 .. autosummary::
    :toctree: generated
@@ -42,9 +43,21 @@ Package overview
    iterable_subprocess
 
 
+Why ``datasalad``?
+------------------
+
+This is a base library for DataLad, hence the name ``Data-sa-Lad``.  The ``sa``
+might stand for "support assemblage", or "smart assets".  More importantly, the
+library is a mixture of more-or-less standalone utilties that "make up the
+salad".
+
+After ~10 years of developing DataLad, these utilities have been factored out
+of the codebase to form a clearer, faster, better documented, and more
+accessible set of building blocks for the next decade.
+
+
 Indices and tables
 ==================
 
 * :ref:`genindex`
-* :ref:`modindex`
 * :ref:`search`