I'm all for a 'de facto' standardisation around a royalty free codec, which is what we get with AV1, but lets not pretend that these companies are doing this for any altruistic reasons.
Everything is moving to streaming, and video usage will only keep growing, so for these huge companies, having what is increasingly a core part of their business in the financial hands of third parties is an extremely unattractive position.
Google was already dead set on leaving this dependency, and now when they started work on their third generation codec (VP10) many other companies started to get the message, prompted in a large part no doubt by the HEVC patent fiasco, which now has resulted in AV1.
>AV1 has a really slow encoder, so until that has changed
Well, optimization has likely only recently started in earnest, given that the bitstream was frozen this summer. Personally I'm more interested in the RAV1e AV1 encoder in the works from Xiph than I am in the 'official' one.