Why do people all over the world prefer .com extension in their domain name?
The original TLDs were developed to offer the user an idea of what the content of the site might be about.
.com = commercial (company/business related)
.net = network (an ISP, for example)
.org = non-profit organizations
.gov = government entities/agencies
.mil = military
.edu = school/university
As you can see, .com makes the most sense for businesses. This is why most companies preferred that TLD to begin with, and now it is considered the norm. Also, that is the only TLD "most" people know, or at least, the first one that comes to mind.