According to Rogers "the performance of your service will improve ... by reducing the modem speed"
So if they want to improve my performance but cutting my speeds by 50%, its seems logical that I should only have to pay half my bill to streamline their accounting. Think of the processing time savings! Less perky decimal places to get in the way. It would improve the performance and the service would improve.
The upload data channel for your node is limited to about 6 megabits/sec for about 300 users. Now this 6 megabits was essentially divided up into about 400k bit segments ... which means that only 15 people uploading can fully saturate the upload channel, which means that downloads will slow dramatically for everyone.
Now, cutting that speed in half means it takes 30 people uploading to saturate the channel ... which is far less likely on a 300 subscriber node.
Cutting the download improves throughput in a similar manner.