Many language implementations divide their JIT into a "baseline JIT" and a "full JIT". A fast interpreter can do the job of the baseline JIT, with faster start

Many language implementations divide their JIT into a "baseline JIT" and a "full JIT". A fast interpreter can do the job of the baseline JIT, with faster startup speed and less latency. Having a good baseline (either a JIT or just a good interpreter) also means that you don't need to rely as much on the full JIT. This is important because it is actually hard to spend 100% of the time in the JIT -- poison pills abound.