It depends on the size of your business and its outreach. If you keep it modest and fear the expense you can go without it, although it is not recommended generally. On the other hand, it doesn't cost you so much to register the other TLDs (TopLevelDomains) or even cc (country code) TLDs to protect your business from possible cybersquatters or competitors driving business away from you.
It's a simple choice between cost and opportunity you have to make. Simple in terms of business logic, of course.