I drive 80 if it is allowed and it´s without danger
Yep, I understand your point a bit but I think it have also a reason why writer-manufacturers not support very low writing speed for high-speed-media. I think 8x should be OK for most 16x-media.
With BD-media it´s a bit different, while my fastest writers support 16x my fastest media is labeled 6x. Here i mostly stay at 4x, but I have some awful media which can´t be burned good overall.