I think cost would be a big factor.....

compare it's price to a Flightmaster with a Tungsten bezel. It can also get scratched but, it's a metal base insert with a clear ceramic coating. I've found it to be much more durable than the MM insert.

With every little detail comes cost. I recently purchased a new Dodge 1ton . As you can imagine, it's not a cheap truck but, it didn't even come with wheel well liners! I had to spend another $80 for 2 plastic inserts.

It seems companies will do what ever they can to cut the initial cost and offer options for extra cash that should have been included. I'm not saying Seiko is a cheap company... if fact, I think they're just the opposite. When competition is the way it is in the world... I guess companies have to do what they can to be competitive.