Why do we pay premium prices for internet, but then we are restricted?!

So I upgraded to the new Gigablast internet, great cool. I previously had 300mbps and then I upgraded and rented the cox modem 3.1. The speeds I was getting were ~450 hardwired, 300 WiFi. I called the technician, they came and took a look and we couldn't get any speeds greater than that. I thought to myself, "why don't I just try a different modem, not provided from cox". So I went out and purchased an Arris Surfboard 3.1 SB8200. I set it up, plugged the bad boy in and BAM, right off the bat my Ethernet speeds were 860-920mbps. Great! Just what I wanted. So I routed 100ft of Cat6 throughout my house for my router that's downstairs and plugged it into the port. Then I plugged my computer's Ethernet cable to the modem on the second port. No internet connection on my computer. I call up Arris Customer service, they say ISPs block the second port and all I have to do is call Cox to have them unblock it. So I call cox tech support, they said they can't do. First lady can't give me a reason why, I asked to be transferred to someone higher up (preferably with a net+ cert or something) and I get someone else. They tell me they can't do it because of some agreement with the Motorola company. MIND YOU, the terrible panoramic modem that I was renting from cox HAD TWO WORKING ETHERNET PORTS! Why am I forced to use your terrible modem with marginally better speeds than the 300mbps. Why am I being punished for wanting to get the speeds I PAY FOR, by being restricted to only one port! My only solution at this point is to hardwire ANOTHER 100FT of cat6 cable from my router BACK TO MY UPSTAIRS COMPUTER. I wish I would have never upgraded.

TL;DR

Cox restricts the second port on a 3rd party modem that far surpasses the cox rental modems. WHY DO YOU PUNISH US?!

On another note, the customer service people that were on the phone with me today were really nice.