Yup, and that's why the rattle so much. Snap on parts are great for the first couple of years, but as tolerance is slowly building up in the connections, things go south quickly.
Now, replace the snap on parts, with pocketed guides and screws for plastic and you've got an interior that won't rattle even after an eternity!
Here's a little write-up on car interiors:
Go back 15 or 20 years and you'll see that car interiors are made from solid pieces. Solid plastic pieces manufactured by injection molding. Injection molding has been a highly precise method to manufacture plastic parts for the last 40 years. Adhesives, on the other hand have only been in the market (read: have been reliable) in the last decade or so. This is the reason that modern interiors use laminated plastic parts quite extensively. You have an inside layer of the worst possible quality of plastic, covered with some elastic layer and then some soft polyurethane based material.
There's a downside to laminated plastics, though. They do not perform well under bending. Actually, they perform terribly and they fail spectacularly, in a failure mode called delamination, where the various layers get separated.
Now, keep in mind that a car chassis, no matter how solid it feels, is a highly flexible structure. A 20000Nm/deg rigidity of the mkI S60 feels like a wet napkin when climbing with one wheel on a curb. A 35000Nm/deg Mercedes will see its doors loose their alignment when you use a jack to change a tyre.
Add to that, that designing parts that snap on one another requires an iterative design procedure in order to find the right tolerances and many, many prototypes in order to get it right.
You, now, understand the sheer brilliance of automotive interiors from some decades ago. Pocketed guides with screws (either for plastic or with metal inserts) meant that plastic parts won't move in relation of one to the other. The flexibility of the interior was based on the flexibility of the solid parts themselves. The interior bits and pieces were free to deform, but not to move.
In a modern automotive interior, laminated parts are not easily deformable. Flexibility is achieved by the means of snap on fitting. One part has a few protuberances, that fit in notches in the next part. It feels solid at first, but as the car gathers miles driving over road irregularities, and the plastic parts have to move relatively in order to follow the chassis deformation, tolerances start to build in the connection, as the protuberance moves in the notch. It doesn't take many years for the protuberance to wear out and the connection to feel as tight as [
highly inappropriate comparison removed].
Of course, such snap on connections are massively cheaper to manufacture and assemble, compared to also adding metal screws and having someone screw them in the production line.
Bottom line, that's why modern car interiors rattle. Because its cheaper, faster and, well,
better.
