It's open for debate, but my view is everybody DOES want every feature they can have.
Not really. If I've got a pickup I use for hauling dirt at work in sketchy neighborhoods I'm going to want a pretty minimal feature set. No point in having a fancy touch screen or satellite radio. If you are buying a car for your mom you might not want that 400HP turbocharged engine but you might want it for yourself along with that fancy rear spoiler wing. Different people have different needs and wants. Similarly many features cost significant cash and adding them can often put the cost of the vehicle out of reach for those of lesser means even if they desire.
Different ranges will cater to different markets (more revenue), but not necessarily more profit.
I think you may not fully understand the economics at work. My apologies if what I'm about to outline is already known to you. I'm a certified accountant and have done some of this work in my day job. This is an over-simplification but more features = more cost to the manufacturer = higher price to customer.
Margins are usually higher with more features but every vehicle has a minimum required profit margin which is typically called a hurdle rate by finance folks. As a general practice the auto maker won't make the car unless they can get at least the hurdle rate margin for it. (the exact rate is arbitrarily chosen but is indexed for the risk of the investment) They also have fixed costs (tooling, assembly lines, salaries, engineering costs, etc) that they need to recoup and which don't change whether they sell 1 vehicle or 1 million vehicles. If they only sell fully pimped out vehicles they are leaving profit on the table because they will have to amortize those fixed costs over fewer vehicles. Even though the might make less margin on the less optioned out vehicle, their unit costs will fall because they sell more of them and can spread their fixed costs over more vehicles.
It's more complex than this but companies maximize profit when when marginal revenue = marginal cost. That is the additional revenue gained from selling one more car just equals the additional cost of selling that one more car. By offering vehicles with fewer options at a lower price point they push out to the point where marginal cost hockey sticks up from over production and increases profit to the manufacturer. Wikipedia has a good article on what is going on.
No. Most cars aren't works of art, because art is one of the few "industries" where uniqueness is key. Save for some limited-edition, luxury cars, that point is moot. Extras rarely value a car, age and exclusivity do.
Has nothing to do with cars being (or not) works of art. People don't (usually) demand that their car be truly unique but they do demand that they be personalized to a significant degree. People choose different paint colors, different engines, different wheels, etc. Car customization is a multi-billion dollar industry both at the OEM and aftermarket levels. I work in the industry and I can assure you that people do not want exactly the same vehicle as the next guy and many are willing to pay to get it. Companies that do not accommodate this to some degree are leaving money on the table. The US manufacturers tend to offer more options and the Japanese less with the Europeans somewhere in between. Even Tesla offers several power trains, trim packages and other options - roughly on par with what you see from the Japanese automakers for certain vehicles.