Many business owners who already preformed their website with their own content as a way to get audience to read their content early, before a website is converted into a website ran by a business,–after strategic planning of their website. Some business owners has bought other businesses, and started rebranding these companies to give them a new lease of life. You can choose to keep a domain name of a business what you bought recently, or migrate it to your subdomain, and rebrand it,–or park an existing domain for your subdomain, or even keep the domain active.
Subdomains always make it easy to save money on domain ownership. For this instance… Walmart chooses to own walmartmoneycard.com for people who use debit cards provided by Walmart. Both of these domains owned by Walmart are common examples via the real world.