The trucks cutting into left lane looks different in different states.
I have seen trucks doing 100 mph in some states. That was in the past years when fuel was less than $1, but still, the vehicles are getting only faster.
So truck changing lane at 70 mph doesn't create much hassle.
But in CA trucks are limited to 55 mph and even most of them do 60, the left lane traffic does 75 when some cars do 85.
When you drive 60 and cut in front of vehicle doing 85, that will make danger situation.
Some truckers just ignore the danger as they feel safe behind 80,000lb of steel.