There are still tons of WebGL apps that make the mistake of loading OBJ, DAE (Collada) files or some similar editor-oriented 3D model format. This is like loading embedding Photoshop PSDs throughout your web page because you don't feel like exporting to PNG. I believe this is a major contributor to the "WebGL is slow to load" impression many users have.

glTF is the PNG of WebGL. It's compact, quick and easy to use. Distributing content in a some other format not optimized for distribution is a disservice to your users, your servers and the technology as a whole.