But it makes the system less complex and easier to handle, as there's one kind of cabling, and complex functions like ABS equivalent are handled from avionics bay
The aircraft braking systems are very complex, including active thermal management and automated braking systems that take multiple data sources to manipulate breaking force, including understand how long the brakes survive when taken beyond melting point (RTO setting on autobrake)
There is approximately zero chance of an aircraft pilot needing to stomp on the brakes because of a random pedestrian or animal, whereas that happens constantly for cars. Cars stop and go all the time and have to avoid each other. Aircraft hardly do that at all when they are on the runway. They use their brakes to not accidentally roll or be blown about, and in the process of landing. Those applications don't need epic response time.
Now consider that the same network used to control the brakes also is sufficient to control every other sensor and servo on the aircraft s well.
I would like to add, brake by wire may be more reliable on planes than cars because planes are maintained very well by experts. Automobile design should strive for simpler and more failsafe options because owners are usually clueless people with limited budgets, who want to do as little maintenance as possible. The fact that hydraulic brakes work so well even in very old cars says a lot about how good they are. When they do get blamed for poor performance, it's usually due to something stupid like the owner not replacing worn out hoses after 20+ years of heavy use. I only found out about that one recently. Old hoses start breaking down and they gradually get congested.
Take a step back and look at how complex brake systems have evolved at the present date:
On one hand, sure, it's just a foot-operated hydraulic pump and four hydraulic actuators.
On the other hand, the ABS module has valves to both cut off each brake caliper and to drain hydraulic pressure from each brake to prevent lockup. In an emergency braking scenario, the foot pump will quickly go the floor as pressure is drained, so the ABS module also has an electrical pump to put fluid back into the system.
All US-legal cars have some form of electronic stability control (and often have lane keep assist), which can use the same components to pressurize one or several brakes to make the car follow the driver's intent (as measured by a steering wheel angle sensor and a body yaw rate sensor. Europe-legal cars also usually some form of emergency brake assist which again uses the ABS module components to apply the brakes automatically.
To keep this all safe, you need pressure sensors to monitor valve and pump functions, sensors to monitor driver input, and sensors to monitor vehicle dynamics.
When you look at the system holistically, as it exists today, it is bandaids on top of bandaids and you realize that you no longer have just a simple hydraulic system.
I would make an analogy to the 737 Max vs. Airbus FbW here: We started with something very simple, and then incrementally increased complexity in (seemingly) appropriate ways. Then, many years later, we realized that our "simple" mechanical system is actually more complex and prone to more complex failure modes than a system which started out complex and rigorously managed that complexity.