Pardon my lack of knowledge about this.
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There are a multitude of reasons:
All wireless communications are subject to interference from everything ranging from weather to intentional interference from adversaries. Fiber optic lines are fragile and can still be tampered with, but anyone seeking to do so must gain physical access to the lines to tamper with them. For example, a foreign nation could broadcast a satellite jamming signal from international waters and disrupt satellite communications across most of the US. There is no equivalent method of disruption for fiber optic cables.
Another reason is that wireless signals are noisy. When you broadcast a wireless signal, you can focus it on a specific area, but some will always bounce around and fly off into places you don’t intend. This means that other wireless equipment using the same frequencies will have to work together to share the frequency. This puts a practical limitation on the number of simultaneous wireless transmitters that can operate in a given area.
Interestingly, you can’t solve this problem entirely by using separate frequencies. Every frequency has something called harmonics. These are adjacent frequencies that “resonate” within the base frequency. The amount of interference caused by harmonics is much less than the base frequency, but it’s still there.
Fiber optic cables contain the signal completely within the cable. So if you need twice the bandwidth, you simply run two cables right next to each other. Fiber optic cables don’t emit any interference, even directly next to each other, so you can pack thousands of them into a single cable, and get millions more times the bandwidth than you could using wireless transmitters.
Then you have the issue of distance. Even at the speed of light, it takes about 1 second to reach the altitude of a geostationary satellite. This means that any communications satellite orbiting in a geostationary orbit will have a minimum round-trip latency of 2 seconds. That’s far too much for something like a phone conversation.
Companies like Starlink are getting around this by operating their satellites at much lower altitudes. To do this, they have to orbit at a very high velocity relative to the Earth’s surface. This means a Starlink satellite isn’t overhead for long. They make up for this by having thousands of them in orbit. They form a constellation, so your equipment is actually connecting to a different satellite every few seconds. You couldn’t handle all of the world’s data traffic this way. The number of satellites required would blot out the sun, and the cost would be tremendous.
All of these issues conspire together to keep good old fashioned cables around, and they’ll continue to be around for centuries to come.
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