It's a brilliant touch. The Model S, when it first arrived, also aimed for a fairly minimalist interior. But some folks complained that it was so minimalist that it came off as insufficiently luxurious — for what was supposed to be a luxury car.
Tesla has since fixed that, making the lastest editions of the Model S far fancier inside.
With the Model 3, is wasn't necessary to aim for luxury credibility. A $35,000 base price meant that the luxury buyer wasn't necessarily customer number one. However, an interior that was all black leather and brushed metal would have been too chilly.
The wood, a Scandinavian touch (we've seen something similar in Volvos of late), provides warmth and texture, tactility. And it definitely feels pleasing to touch.
For what it's worth, the quality of the plastics, often a sticking point in less-expensive vehicles, is quite high in the Model 3. Our tester also featured some lovely light gray and black Alcantara throughout, and although Tesla has since dropped the material, a type of synthetic suede, it also added yet another a nice tactile vibe.