It might be that they're in the top 10% of interest in ramping up in these types of things. I'm sure I'm not alone in having little interest in attending a technical conference that mostly covers things I already know - I'm there either to learn, in which case I want new content - not rehashed content - or I'm there for other reasons. Low rates of already using these tools, then, may make a certain amount of sense. If they were already putting them to practice, they may be less likely to attend.

Or I could be way off base - I've never attended CppCon. And I do love me some ASAN when I need it ;)