The Dell XPS line only has Thunderbolt USB-C data ports. So for functional and aesthetic reasons you'll have a port on both sides.

Compare with a more mainstream business or consumer laptop which in addition to two USB-C ports may have HDMI, multiple USB-A and maybe Ethernet jack. What ports should go on what sides? It often comes down to cost and routing limitations.

Each USB-C port needs a PD Controller IC which needs to be placed somewhere near the port. They come in either single or dual port capabilities. One dual port PD controller is less cost than two single port PD controller.

Also the Thunderbolt architecture in most notebooks has the controller in the CPU and a retimer IC right next to the port. Depending on whether or not the CPU is centered (left to right) and the size of the laptop then the USB-C port that is furthest from the CPU may require a second retimer IC to ensure signal integrity. This impact both routing and cost.