Modern Linux systems (with udev or devtmpfs) create device entries for every device that is present on the system. All the virtual consoles are always present (whether they’re active or not), so all entries are created.

Why are there multiple tty?

In the past many computer systems would come with serial port. Nowadays, this could mostly be found on server type of computers. Multiple ttyS devices could be useful with RS-232 hubs, which allow connecting multiple devices to be managed via USB or Ethernet.

How many tty are there in Linux?

By default, there are 7 ttys in Linux. They are known as tty1, tty2….. tty7. The 1 to 6 ttys are command line only.