Recent versions of Mesos (and all versions going forward) have slaves with checkpointing turned on by default, so  Spark should get allocated resources either way. That being said, the only real reason to use this feature in Mesos is if you often have Spark jobs that run a long time and you'd like to be able to restart a Mesos slave without killing the Spark job that's running. Assuming Spark jobs finish often enough (or can deal with the occasional failed/restarted slave) it might not be worth paying the extra overhead on the slave to checkpoint information for Spark.

Of course, I think wiring this up and letting the end user decide is great!