[Wowfunhappy]

I would say PDFs are actually reasonably consistent though. Weird things happen on occasion, but I've certainly had more success than with SVGs.

[auxiliarymoose]

They are reasonably consistent because there is a de-facto reference implementation (Adobe Acrobat) which, if your implementation does not match exactly, users will think your implementation is broken.

There isn't such an implementation for SVG.