Because it's their company. If I was the CEO of a company, I'd want the freedom to offer whatever services I wanted, at whatever prices I wanted. Shouldn't you have the right to have control in your own business without the government interfering? No one ISP owns or controls the internet. Even in areas where there are monopolies, there are options. I only get Spectrum here, but there are smaller internet/satellite internet companies. Most phone providers have options, as a larger chunk of all internet traffic comes from mobile with each passing year.
I'm not FOR the cable companies. I think they suck and charge way too much money as it is, so this isn't about being their supporter.
It's like Netflix. There are payment tiers. If you want to use normal Netflix, it's one price. If you want premium HD streaming, it's a higher price. If you want DVDs, it's another. I don't see anything wrong with structuring things that way. If the government steps in and says Netflix can't charge more for HD premium streaming, than HD premium streaming might not exist.
Let the people decide what they want and what they don't want. If businesses decide to sell out to companies or join them to force monopolies, that's their business. They should be able to run things as they see fit. It opens the door for better innovations. If the government can control who can do what and how much they can charge for it, that not only stifles innovation, but it handcuffs businesses.
Again, I'm not for monopolies either. Just because you fight for the rights of others to freely run their business according to their own models doesn't mean your pro-monopoly. Fear mongering about what companies 'might' do isn't a valid reason to create a law that handcuffs companies. If it's something like health regulations that involves the safety of others, that's one thing. But spreading fear that the internet companies *might* charge you more for a premium service isn't that.