An year ago I started dualbooting Elementary as my daily *nix OS. All was well, until one day, with no hardware change or OS update, the touchpad stopped working. I'm back to VMs now.
If I wasn't dualbooting I might have spent more than a day to figure out what happened - but I was too lazy and scrapped dualbooting.
My understanding is that there was a kernel change that borked touchpads this year on many distros and that the change was related to the Synaptics driver seeing little love over the past several years. [1] It looks like the folks who care (like Alps) have been patching over corner cases off and on and as recently as last month.
If I wasn't dualbooting I might have spent more than a day to figure out what happened - but I was too lazy and scrapped dualbooting.