Only for a weak definition of "solved". As mentioned above, context switching is expensive and extra L1 cache is valuable. Time-sharing can also have a huge e

Only for a weak definition of "solved". As mentioned above, context switching is expensive and extra L1 cache is valuable. Time-sharing can also have a huge effect on latency (because requests must wait until their server is scheduled), even when the throughput is still good. Even if time-sharing performs well most of the time, when it goes wrong, the performance problems can be opaque and hard to debug. In general solution that "really" does something will save engineer-days as compared to a thing that does it at the same price/performance trade-off, but virtually.