Sorry for the necro.
I was just thinking about VMs sending the trim command to the virtual disk driver, as it could be used to automatically shrink virtual disk images.
It turns out there is no performance benefit on SSDs (because wear leveling will cause new rights/rewrites to have identical performance, so long as the host disk itself isn't full), while on HDDs you could end up with excess fragmentation.
So, the only benefit is that virtual disk images could automatically shrink, but the benefit to most production machines is minimal - disk usage generally increases with time. It would be a convenience feature for a developer or hobbyist, and that's about it.