Is there one or more package(s) which appear to be the most commonly-used commercial integrated general purpose accounting software used by small businesses?

RQ1: Is the adoption of commercial integrated general-purpose accounting software as ubiquitous as the literature seems to assume?
RQ 2: Is there one or more package(s) which appear to be the most commonly-used commercial integrated general purpose accounting software used by small businesses?
RQ 3: Why did small businesses choose their particular accounting software packages over other packages, or decide not to use such packages at all?