First of all, you have to know What is the gateway.
Gateway: The equipment connects the two network segments with different protocols.
Its role is to translate the data of the two network segments with different transport protocols.
Not only limited with .1 suffix ip as the gateway. In other words, if you are in the LAN, the gateway can be set.
Setting .1.1 suffix ip is just a matter of habit and default router address is generally .1 suffix. So it became a habit.
If necessary, you can modify it into 192.168.1.2.