Here's why:

* No creation or destruction: At a sliding (transform) boundary, tectonic plates slide past each other horizontally. This movement doesn't involve the creation of new crust (like at divergent boundaries) or the destruction of existing crust (like at convergent boundaries).

* The nuance: While the plates themselves aren't being created or destroyed, some minor changes can occur:

* Faulting: The sliding motion can cause fractures (faults) in the crust, which might lead to small-scale changes in the crust's structure.

* Uplift and subsidence: The pressure and friction from the sliding can sometimes cause parts of the crust to be uplifted or subside.

In summary: While the main processes of crust creation and destruction are absent at transform boundaries, some minor changes in the crust's structure can occur due to the forces involved.