This is only true if you have sys-net set to autostart on boot. I should have mentioned that I do not have any qubes set to autostart. You can use this command to see whether or not a qube is set to autostart:
qvm-prefs sys-net autostart
For my use, I have created panel buttons to start and shutdown all of my service qubes. I have a sys-net qube for ethernet networking, a sys-wifi qube for Wifi networking, a sys-usb qube for usb management, a sys-usbnet qube for usb networking, a sys-audio qube for audio management, and then sys-whonix and a few firewall qubes. There is a lot of customization that can be done in qubes. I prefer my system to boot as quickly as possible, allowing me to decide exactly which qubes boot and when.
To create my start and shutdown buttons, I made launcher items in the panel that execute a script for the given function, and the script is just the qubes command to start or shutdown the qube:
qvm-start --quiet sys-net
qvm-shutdown --wait sys-net
You could also input the command itself instead of using scripts, but I use scripts in order to make restoring backups easier.