Is it necessary for every business to be a unicorn? I don't think so and I strongly suggest people build "boring" businesses instead.
"Boring", however depends on your view.
Not every company needs to have a plan to become a unicorn, have thousands of employees, have a billion dollar recurring revenue, need not be the on the cutting edge of technology, or be on the lookout for the next fix (series G funding for e.g.), or even be known as the path breaker in the field.
I'd rather run a boring business, serve a need that other people pay for, have happy employees, does not need funding and gets you financial independence.
If you are still looking to build that Unicorn, building boring companies also lets you build more experience, with limited financial risks, and provides you the revenue needed to experiment on that billion dollar idea of yours.