I’m studying multithreading, and I came across that it is preferable to use async() with io_context . But I don’t quite understand why they are needed. I re-read several documentations and watched many lectures on this topic, but I still couldn’t figure out what the difference, for example, in this code:

boost::asio::io_context io;

io.post([](){ 
   do_some_work() 
});

std::thread thread([&io]() {
 io.run();
});

from this:

std::thread thread([&io]() {
 do_some_work();
});

I also saw many examples of using io_context with async in client-server interaction with so-called handlers. But I just don’t understand their meaning. Why are they needed if you can just write methods in a row:

socket();
connect();
read();
handle();

Why use a complex async construction with io_context, if you can write everything structurally (as I did above) using future/promise and it will be readable and understandable?