That's unfortunate. I think it has to do with the fact that most people prefer doing things the easy way, instead of the most efficient way. So they want some simple measures to show them the CPU, Memory usage and some other straightforward things in a nice way instead of bothering with more complex things, available in more "sophisticated" plugins. It's a wicked world, sometimes good looking things take precedence over more elaborated and more reliable things - it's not the first time I notice that...
Other than that, I think it has to do with the fact that currently there are not many skins that actually use your plugin. The more skins use a plugin, the more used and searched for is that plugin - that's my impression, at least.
Plus, there's the fact that most of the computer stats are available without using Windows PerfMon capabilities at all. Those PerfMon capabilities are essential in some specific cases. For example, before using Rainmeter, I wasn't actually quite aware of PerfMon or WMI...
But you shouldn't be discouraged - good things were always used and appreciated by few at the beginning. Think television, computers, the internet : they all started slow, gaining momentum over time. So I expect 10 years from now, 1 in 10 Windows computer would use your NomFerp plugin in Rainmeter
P.S. I take a different approach in my projects : I always start them to suit my needs first and foremost and then, if others like them or use them, great. If not, at least I'm happy as they made my tasks easier/more efficient/etc. That way I'm never really bothered by "the reception" they get. But then...that's just me. Others need to feel appreciated more...