You might be surprised to know how many different oil systems (with and without filters) most cars have in addition to the engine crankcase oil. Transmission oil, steering fluid, brake fluid, differential oil, etc. Electric cars might do away with the big one but those other systems all remain.
Though it is a single speed, Teslas do have a reduction gearset that does eventually require oil replacement just like a manual transmission. By adding a filter to the Model 3, Tesla can greatly extend the time before this is needed.
I am just surprised at the accessibility of the filter. I remember trying to change the lubricant in the differential of my '69 TR6. Damn near impossible. Watching the tear down videos I am generally impressed with how easy it seems to be to get to all the things that will eventually need service. Pretty impressive.