I use PDFs for engineering drawings of mechanical parts. It's been done for a long time and is a good fit. There's a specific sheet format and scale, and is meant to be able to be printed easily
(If you're using PDFs for precisely-scaled engineering drawings, I expect you're well aware of this and have a workflow that avoids scaling, but I see people trip over it all too often.)
Good for you, but that doesn't change that most of the uses of PDF on the web aren't for applications like that.