I would guess that the Thrototling is a business decision in order to find more incremental revenue. In order for business's to grow they must sell more of what they have, improvements to what they have or find new streams of revenue.
[Or you could say bringing in the sheep] which is what we really are. By throttling they have new revenue streams and ones that are not visable to the user. What a great scam. The problem is that our air waves fall under Government controls and the Cable Co's are smart enough to know that enough private citizens will not get together to force the Gov't to take actiona and I am guessing these Companies have a ton of Lobyist sitting in Local, State and National Gov't to prevent fairness to the user.