You can create a multisite network without WP Ultimo using the native multisite features in WordPress.
But the default sign up process is very lacking, so we recommend you use WP Ultimo because it provides many good features for your business:
- It provides a pricing table
- It provides the billing feature to charge your users monthly or annually for each site
- It provides a better sign up process
- It provides a site templates feature, so new sites are copied of pre-configured sites
- And much more
Also, WP Frontend Admin has a great integration with WP Ultimo, so you can create dashboard pages for specific billing plans, etc.
Those are the reasons why we mention WP Ultimo in our tutorials.