It costs money that consumers don't have, especially in a recession, to continually change and update the products in visible ways. Legacy auto played this game and, sure, we often got new-looking cars each new model year but then they cut corners on quality to pay for it. We ended up with a race for the bottom. And then the Japanese cars came in, plain and unassuming but high quality and practical at an affordable price, and they cleaned up.
Model 3 has a rumored update coming, I think it's in Q3, and it's likely mostly to reduce manufacturing expense. They will probably take the opportunity to update aesthetics while they are at it. I love the way Elon understands the path to success is a great product at a great price. It sounds simple but so many forget that it costs money to make changes simply to "freshen the look up" and the consumer has to pay for it. Most people just want a car that they can afford and is reliable. Look how successful the Model T was, the VW Beetle, the Toyota Corolla, etc. Most of the cars I see on the road today are not "peacock cars" they are just plain and practical, that's what most people want and are willing to pay for.