Not all software are webapps (though I agree versioning is much less important, particularly for the end user, in those cases).
For those of us writing enterprise software that gets installed/ran by customers versioning is pretty important:
* Unlike a website not all our customers are using the same version, so when a bug is reported we need to know what version it was encountered.
* Customers need to know if version X of product A is compatible with version Y of product B.
* Gives customers an idea of the magnitude of changes, e.g. bumping the minor version will usually indicate mostly bug fixes, security updates, and small/non-API-breaking features.
* Facilitates easier communication with QA, beta testers, etc than referring (only) to a build.