Most notebook PCs have their WiFi antenna located in the:

The LCD panel itself is the display screen; while it is housed in the same lid, the antenna is embedded in the surrounding bezel, not within the LCD module.

The WiFi card contains the radio transceiver and is typically located in a Mini PCIe or M.2 slot on the motherboard, not where the antenna is physically routed.

The I/O area is on the sides or rear of the chassis and is surrounded by metal, which would severely degrade antenna performance.

Routing the antenna wires through the hinge and into the display lid places them as far as possible from the metal chassis and internal components, which would otherwise attenuate the wireless signal. The plastic bezel of the lid provides a clear, unobstructed path for RF transmission.