"Informally, a strategy profile is a Nash equilibrium if no player can do better by unilaterally changing his or her strategy. To see what this means, imagine that each player is told the strategies of the others. Suppose then that each player asks themselves: 'Knowing the strategies of the other players, and treating the strategies of the other players as set in stone, can I benefit by changing my strategy?'
If any player could answer "Yes", then that set of strategies is not a Nash equilibrium. But if every player prefers not to switch (or is indifferent between switching and not) then the strategy profile is a Nash equilibrium. Thus, each strategy in a Nash equilibrium is a best response to all other strategies in that equilibrium.
The Nash equilibrium may sometimes appear non-rational in a third-person perspective. This is because a Nash equilibrium is not necessarily Pareto optimal."
Rather the word-processing situation (and likely the QuickBooks situation, though I know much less about accounting software) seems to be something like maximizing the lowering of perceived entry cost (in terms of learning to use the software) over all other factors (with resulting increasing in complexity for more advanced functions and poor flexibility).
> Very few are going to be able to deal with a text file of journal entries. QuickBooks is the standard for all small business accounting, like it or not.
I always find this lowest-common-denominator as de facto standard depressing. It's how we end up with word processing documents as a standard for exchange and collaboration (and word processors are horrible environments to create in).