Why would they? Some added DisplayPort before HDMI 2.0 was ready, but it will likely disappear from tvs once again. Other than computers, what AV equipment includes DisplayPort?
HDMI 2.0 should be on every new computer soon. Can't hang onto the old things forever! Everyone will be wanting USB 3.1 and USB-C soon also.
I agree with you that HDMI 2.0 should be on almost new system in the future but it isn't soon as fast as you think. You can see on the some top devices have just released in 2015 as macbook pro mid 2015, macbook 12 inch, ... where is the hdmi port 2.0? Obviously, at this time DP 1.2 or mini DP 1.2 are enormous common than HDMI 2.0.