I believe four oz. is considered a portion of steak. I think Americans have gotten way off-kilter in their ideas about portion sizes. For example, I believe it wasn't until the late 1970s or so that McDonald's started offering medium- and large-size french fries. People just ate the regular size, which is the current small size, and that was fine. But then McDonald's realized they could sell more fries if they offered larger sizes, because while many people felt piggy ordering two smalls, they were comfortable ordering mediums or larges. Now a small seems like something made for a toddler.
That's one example of a trend that happened in a lot of different places, from bagels to big gulps to giant candy bars to restaurant portions in general and so on.
I saw a magazine article about a guy who lost weight simply by reducing the size of his plates from 12 inches to 9 inches. Apparently he has written a book about it. He moved into a 1940s house, and found his 12" dishes didn't fit in the cupboards!
I could relate, because I moved into a smallish 1940s house, and bought a 76-inch sofa, and the delivery guys couldn't get it in the front door. I had to exchange it for a 72-inch or something. But some furniture stores simply don't sell sofas at less than 80 inches. Now this week, I've been shopping for a new refrigerator. The placement of the cupboard above the fridge limits me to one smaller than 67 inches high. Those are very difficult to find, these days -- I finally found a few, but they have to be special ordered. The current fridge is, I'm guessing, maybe 20 years old, and is less than 60" high, which practically constitutes a dorm-size compact these days.
Everything is just bigger now.