I'll point out that there's a really good use for leaving the Guest account enabled, primarily on a portable
If a thief gets a hold of the machine it allows them to use it, possibly allowing you enough opportunity to get it back via "Find My Mac". Alternative if they have a bit of smarts is that they just nuke it because they can't get into it any other way. Lets face it, most thieves are lazy, so enabling their demise is essentially chlorine in the gene pool 🙂.