Is it just the younger generation? I’ve seen all generations favour their phone over a laptop for anything that needs to be done online. Which is basically everything.
Everyone is gravitating to the phone, but habit is an enduring force. Some people will always use a computer for specific tasks as they learned for the rest of their life. I think most of us are in that camp.
Most people really do not need the dedicated device, whether it's a laptop or desktop, to use the Internet they way they want to.