The vast majority of the commercial cattlemen I know couldn't even begin to tell you what birthweights their bulls were when they were born. Most don't care as long as their mature cows can have unassisted babies. They are using Angus bulls, Simi bulls, Charolais bulls, Limi bulls, and on and on with all varieties and colors of cows. With the exception of SOME Angus cattle, most commercial cattlemen consider registered animals to be playthings of people with more money than sense.
So, the "steer" people who just judge calving ease by whether a cow can have the calf without help or not are probably closer to the real world than purebred breeders.
Honestly, when I hear commercial cattlemen in our region talking about calving ease, they are usually griping that there is too big of a swing toward "calving ease" bulls. If you start reading advertisements closely, you'll notice a lot more talking about moderate calving ease than "low birth weight" bulls.
I have no idea what our average birthweight is for sure, but I'd guesstimate it in the 80-90 lb range.