[RomP]

This has been answered million times: besides the historical reasons (which are extremely powerful), it's performance. Performance not as in how fast would it take to calculate this, but performance as in what is the worst case scenario for calculating this. Think Garbage Collector, mostly. But also think ability to control exactly how the data represented and stored in memory. Tighter storage == fewer cache misses. Market moves away while fluffy managed data travels from RAM -> cache -> CPU.