Is there a reason not to use H265 and VP9 over their predecessors other than compatibility?
Why would that be a bad thing? I would think being able to utilize your entire CPU would be a good thing. If it's only using 30% of my CPu that means it's not going as fast as it can.
Massive encoding times
Higher decoding complexity
Inefficient in comparison to h264
libvpx is still slow as fuck
H265 is full of patent cancer, remember the two licensing pools thinge?
libvpx and x265 encode at similar speeds and produce similar looking results.
Currently VP9 decodes much faster than H.265 because much more effort has been spent on VP9 decoders than H.265 ones.
Takes more computing power to encode and decode.
Not sure if parodying memory-hog apologists. Aside from the 100% scale, 30% usually means a poorly-threaded task is maxing out one thread/core, and the OS isn't always smart enough route other tasks to idle cores.