Well, basically, most applications that you want to write are basically 90 percent rdbms with a thin layer on top for the views (usually php etc.). The 'power' of lisp isn't relevant. Other types of applications are usually performance critical and written in c etc, or glue code written in languages with libraries tcl/perl/python etc.

So basically the traditional niche of lisp, complex apps, has been replaced by sql.

There are apps written in lisp, like this site for example, but that's just for vanity mainly (pg is famous for his lisp books) - it would be have been easier to write it in sql.