A lot of technology gets built through layering new systems on top of old ones to the point where some stacks look like an archeological dig at Troy. There is nothing wrong with that approach per se, except that over time some of the lower layers become a constraint on what can be done above them. A classic example of that has been operating systems. Sometimes they have to be revised, for instance to account for the move from 32-bit to 64-bit architectures. Sometimes they have to be replaced ...
