Understandably, SQL Server (like most products?) is still catering for the majority of customers. Perhaps changes like SSDs would require would best be offered as an alternative side-by-side engine implementation. By that I mean that Microsoft, and the respective vendors of other products, would supply both engines in the product either of which could be selected to use. The selection could be either automatic or configurable or, even possibly, both.

EDIT: "configurable configurable" just didn't make sense 😉