When I think "high-end helmets", the brands that come to mind are Arai, AGV, Bell, Shark and Shoei. Comparing these brands over the last few years, all of the brands mentioned have released new, ground-up designs except one: Arai. For me it looked like Arai was being passed by their competition because they had not followed everyone else and released their own "all-new" design. Why hasn't the motorcycle helmet industry leader that introduced their first Arai RX-7 Helmet in 1977 delivered a new shell shape like everyone else has?
In this group picture of all the RX-7 / Corsair Helmets that have been imported into the US, anyone can see how similar they look to one another. At a glance it looks like a lack of progress from Arai. The reality is this represents their commitment to building what they feel is the best motorcycle helmet in the world. For Arai Helmets, the Shell Shape is the foundation of everything they do. Arai Helmets all use their Round R75 Design built in the organic shape of the human head working to maintain a relatively uniform thickness at all points.
Over the years Arai has constantly refined their design to improve rider safety and comfort while staying true to their core principles. They have collected a ton of data since the first RX-7RR3 came to the US in 1996 which has been used to make advances in both rider safety and performance. Radically changing the shape would make much of the data they have irrelevant. Making a helmet that performs in a real world motorcycle crash takes more than just passing a helmet certification test.