Let's discuss the defaults for the "Tapping" option again
- if you don’t know that tapping is a thing (or enabled by default), you get spurious button events that make the desktop feel buggy
I've never encountered any "bugginess" or any other issues when this option is enabled by default, meanwhile this feature has been turned on by default for the past 15+ years for all Windows/MacOS laptops, all smartphones and tablets. Over 98% of users expect this feature to be enabled by default.
- if you do know what tapping is and you want it, you usually know where to enable it, or at least you can search for it.
It's a really good question. Say a user comes from Windows/MacOS X and he expects this feature to be enabled by default. He then either thinks that his touchpad is malfunctioning in Linux (not a good first impression) or goes to Google and types: "tap to click ubuntu". Now I can't say the first hit on Google is exactly correct ( https://askubuntu.com/questions/971517/synaptics-touchpad-tap-to-click-is-not-working-in-ubuntu-16-04-lts-gnome ) and works in all cases which means a lot of frustration.
The industry standard for this feature was established a long time ago. In light of this I think it makes perfect sense to enable this option by default and leave it configurable for the users wishing to get a different behaviour.