It is a commercial thing.....

The Neurnberg toyfair is leading in this, most big factories are using this fair to show their latest models. Customers (for sure we: the onroad RC racers) are very sensitive for "new products" so the manufacturers have to come up with something new or else the customer goes to another brand who does have something new.

And face it, if an engine is very competive, why would you change it?
Thats why most brands are working on the looks. They are lowering the head and making more and bigger cuts and grooves inside the engine because we think it makes the engine better.