Because cars are quite complex and they move around they are time consuming and expensive to animate. Especially if a car turns and rotates relative to the camera, that is quite the job. They also are an object with familiar geometry so it needs to look correct and consistent, unlike character heads and faces for which we accept a lot of artistic liberty to be taken.

It comes down to some options:

• draw it well (takes a lot of resources)
• CGI but integrated very well by tracing over it by hand (also expensive)
• draw it using reasonable resources (probably won’t turn out very well)
• CGI but don’t redraw each frame (CGI will jump out as being CGI)

I remember the first episode of Non Non Biyori. Beautiful intro, one of my favorite introduction moments. The only thing that takes me out of it a bit are those ugly ass CGI cars lol. They really stand out!

For an example of good car animation? I don’t watch much things with cars in it but in Lucky Star episode 6 it starts off well. They are either drawn or CGI that is traced over. When the initial D parody starts, the outside of it is clearly CGI, but the inside is drawn/traced. When you see the camera panning around the car, you can see that it would take a lot of time to trace each frame to make it blend into the art style and background. Maybe the CGI look has to do with the anime they are referencing, I didn’t watch it.