Well, only bandwidth within their own wires to the cable company.

When you use the internet, it's likely that your cable company is then routing traffic as a middleman, paying a Tier 1 Network (unless they are a Tier 1 Network like AT&T, or somewhere in-between with peering agreements).

Basically, they may or may not be paying a usage rate (by the byte, as it were) to someone else in order to serve you that internet, and their bandwidth to internet in general is far less than what they deliver when it comes to TV.

With TV, they're receiving the entirety of all their channels regardless of who is (or isn't) watching them. They then internally host each channel on their servers, relaying it to each user as requested.

TV takes up bandwidth on the lines, but it's a reserved frequency for your box usage. they have enough bands to support everyone in their network, so they don't need to free up the frequency channel when it isn't in use. They may do this, but in reality the boxes are pretty much always reserving a connection when the box is booted (so that it's quick to turn on/off).

*TL;DR - *. Internet is more steps and has a need for bandwidth shaping. Their TV signal never connects outside their own network, and costs them only a bit of electricity to send out.

If enough devices are all in use, the signal may be dropped in nitrate to fully support all users, but this is rarely the case (even accounting for boxes left). The main reason to build in a shut off feature would be for electricity savings / with efficiency.