So it is disingenuous to complain that your top speed means you burn up your allocation. It's unlikely anyone is happy to pay per Mbps, so they gotta work out something which requires compromise.
Now, the limits are tiny, the pricing nuts, etc., but it's not fundamentally a terrible model. On cell data, I'm very happy to buy per GB so I can decide how much to spend.
The real downside is that capping users or offering low cap plans stifles innovation. It sounds nice to be able to "pay what you use" but that has a negative impact overall.