If you have .net domain, and another guy has a website about the same thing with a .com domain, you will be driving traffic to his site. For many people .com is the "default" domain. He will be very happy about that and will be your great fan.
It just getting more and more pupular lol
I guess from the beginning .com is the extension that more people use than others, then people just follow the trend and use .com so now it it the most popular
.Com is the most popular, it has been for a long time. That is like a trend of consuming. The customer is likely default easier to remember the domain like sample.com ( .net ) than other .extension.
Nowaday, there're more domain extension like: .xyz, .asia, .ninja, .home, .club, .online, .mobi, .me, .website, .today, .tv, etc ... for customers of business/ individual to choose.
I think the trend will be differrent, because the source of nice-name .com is limited. The best way is choosing .others that fits the business/individual.