system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 Why did video games only work on channel 3?
gpt
Early video game consoles had to use an RF analog signal to transmit a signal to a TV because dedicated analog and digital inputs like RCA, HDMI, and Component either weren't common place or hadn't been invented yet.

External devices like Video Game consoles, PVRs, VCRs, and DVD/BlueRay players weren't a consideration in those days so TVs either had an antenna hook up or a Coax for cable and that was it.

Very Early consoles like the Atari had a switch box that would plug into the antenna port (2 screws) on the back of a TV and would bypass the Antenna when the game console was running.

80's consoles like the Nintendo used a similar device that bypassed the cable coax because coax ports had since become standard on TVs. So you would plug the Nintendos gizmo in between the TV and the Cable TV cable. (The NES also came with an antenna screws to Coax adapter just in case) But because cable TV sends signals on multiple frequencies (each channel) the Nintendo's gizmo had to chose which channel to use. So they decided on Channel 3 and Channel 4 as they were the lowest channels and therefore compatible with every television set. There was a switch on the gizmo to switch between channel 3 and 4.

The Nintendo also had RCA video and audio out ports that would later become the standard for video game consoles until Component and HDMI cables became the norm.