If I only lost while gambling 20% of the time, I would be ecstatic. Meanwhile in my job as a consultant, I get paid 30% of what my clients are actually billed. Uber takes 20%. My employer takes 70%. I fail to see the outrage.
What percentage do the cab companies take from their drivers?
You misinterpreted the poker analogy. When 20% is taken out of every pot, that includes the ones you lose. It doesn't mean you win with an 80% rate. When the rake is 20%, basically half the entire table's money is gone after 3-4 hours. (If you're going to criticize an analogy, you better understand the analogy.)
Many mobile developers defend Apple taking their 30% cut.