I presume it was there for the same reason we still get a memory checker with Windows 10. Sometimes memory is just plain broken. If it's toward the bottom of the list of memory locations, it will get used a lot so you'll notice very quickly. If it's up at the high end, though, you may not noticed unless you load some very large programs.
There's different ways memory can break. Faster checks do the easy ones which will catch a lot of problems but not all. Slower checks catch more problems but take a longer time.
Though, once you've had your PC for a few weeks, it isn't likely memory is going to break any time soon. There's really no point in checking any more unless you start seeing issues. Or you miss watching your hard drive get defragmented so much that you're willing to try anything.