Over 50% of my DNS queries get blocked by the pihole [0]; and I've seen it much higher. Like you said, it's one of the most prized devices on my network.
That's fascinating.. I would love to know what the averages are across a wider range of users..
In contrast, For my home network, it's just under 15% of queries that get blocked. I've got 3 Macs, a Windows 10 machine, an Apple TV (all connected 24/7) and a handful of iOS devices that hop on and off the network.
I get about 15% of queries blocked with 3 Windows laptops, 2 Android phones, 1 iPhone, and a smart TV. I do run most of the traffic generated for work through work VPN though, and that tends to be the largest source of traffic (about 80% by data volume), which completely ignores local DNS.
[0] https://i.imgur.com/dPZzYjL.png