This is a beautiful quote because it is an example of one industry's bad behavior leading to another industry's bad behavior, upon which the first industry then users the second's similarity to justify themselves. Cars only started doing this because phones made it normal. It's wrong in both cases.
It's similar to when Apple defended it's 30% store cut by claiming it's an "industry standard"... specifically, an industry standard that Apple established.
Steam also don't engage in anti-competitive behavior and prevent billions of people from using alternative game distribution methods like Apple does.
What we need is real competition in the mobile app distribution market to determine whether or not that 30% is actually fair, efficient and competitive. As it stands, there is no competition in mobile app distribution.
If you try doing it for any PC games released over the past decade, you are more likely than not gonna have a disk with some installable files and a Steam code in the box. Without that Steam code, there is no way for you to play the game.
At this point, there isn't any difference between buying directly from Steam, as opposed to "walking into Best Buy and buying the game you want off the shelf".
What's the point if you (as a customer) end up paying the same price at the end of the day anyway, and you still have to use Steam DRM? The only difference in your case is that the cut is going to Best Buy instead of Steam.