Hi,
Compressed textures can be used with Verge3D, although programmatically.
DDS: https://cdn.soft8soft.com/demo/examples/index.html?q=compressed#webgl_materials_texture_compressed
PVR: https://cdn.soft8soft.com/demo/examples/index.html?q=pvr#webgl_materials_texture_pvrtc
(no ETC example)
The compressed textures are very good in saving video memory in runtime. Unfortunately, from our past experience they appeared to be less effective with regard to file size, since JPEG and PNG are more web-friendly and well suited for transmitting over network connections.
Another drawback is that these compression formats are only supported for a fraction of user computers or devices: DXT (WEBGL_compressed_texture_s3tc) is only supported on desktops, PVR (WEBGL_compressed_texture_pvrtc) is mainly available for iOS, and ETC (WEBGL_compressed_texture_etc) also only works for mobile.
The ecosystem therefore is very fragmented and requires using different converters in order to use them.