Problem: When multiple layers are highlighted, the Transform tool will only transform one of the layers. The same restriction applies when something on the canvas is selected. Transforming them all is only possible when the desired layers are all inside a Group.
Solution: Allow the Transform tool to transform multiple layers regardless of whether or not they are in a Group Layer.
Why: A common workaround is to put the layers inside a Group Layer. The issue with this workaround is that you need to disregard your preferred layer organization simply to transform multiple layers. You then have to put the layers back in their original place once you are done Transforming if you wish to retain your original layer setup. This can slow you down and throw you off if your workflow involves transforming a lot of layers in different locations. The slowing down is exponentially worse the more layers you have to transform.
In addition, if you want to transform canvas selections involving multiple layers, you have to cut and paste the selection for each layer one-by-one into a group layer and then merge these pastes back to their original layers once you’re done if you wish to preserve the original layer setup. Again, a slow process.
Someone might say, “Just merge the layers to make it easier,” but that’s not a route one can take if you need all your layers to remain intact.