I think they should still add cars to The Sims 4. I don't think they could give any time management benefits or be used around the neighborhood but the game could give sims bonuses or something I guess, like using a car gives you a well rested moodlet or something when you travel with them.
While I understand that cars would not fill a large role in The Sims 4 engine, I still find it incredibly immersion breaking that we can't own cars and that there are no public transportation or vehicles for law enforcement or the fire department.