This might be true if cable companies did not make a profit.
In the US, at least, I think the lack of competition (almost monopoly pricing in most areas) has led to exactly the opposite situation - plenty of profits for the cable providers.
Do you have evidence for the claim that the monthly fees are not enough to cover the cost of providing the service?
I tried to find numbers but couldn’t, so I’m left with a macroeconomic argument. Better details would be welcome.
You were splitting that cost with the advertisers.
This is not a defence of advertising, just a reality check on this bad example.