RIM's focus has always been on corporate users. That means IT Departments and budgets. The general consumer Blackberry like the Pearl and Curve have been around only for the last couple of years and still remain secondary to the corporate user in RIM's business plan. I don't think they're going to devote the resources to create a high end luxury model when their core customers are focused on completely different areas.

I myself am fairly impressed with the quality of recent Blackberrys. My Curve and 8800 are both rock solid in build quality as well as with software stability. If you're so tough on your Blackberrys that you find yourself replacing them often you might consider a ruggedized solution like an Otter Box.