Note that by previous internet usage patterns the sustained usage of an shared upstream connection wouldn't necessarily result in less than maximum speed if provisioned correctly based on usage levels. That may be different now with more video streaming, but only in scale, not in principle.
You are paying for a given usage profile, and the economics are based around that usage profile. A few leaches can exist for a given economic expectation, but beyond that everyone suffers.
Leaches, wtf?
Should the power company be able too ban you from using the electricity they sell you to power a saw? If you do, are you then leeching from the other electricity customers?
Just because you purchased 800 square feet (or 1Gbps), doesn't mean you can do whatever you want with it.
Any legal device connecting to any legal service so long as you don't harm the network.
Why? Really why? I'm buying a certain number of bits per second. They don't need to know nor should care about the content of those bits.
If they oversubscribe and sell bandwidth "bursting" up to X, but only a small fraction of X for a sustained period then they should have to advertise that clearly and not claim "X bandwidth connection". Rather than burying it in a TOS.