It's because users are used to multi-words companies being a single word in a domain (i.e no hyphen). So when people type your domain a non-insignificant percen

It's because users are used to multi-words companies being a single word in a domain (i.e no hyphen). So when people type your domain a non-insignificant percentage of users are going to type it without the hyphen. If you buy both domains (with and without the hyphen) and 301 redirect the hyphenless domain to the hyphen'd one you'd get over the worst of the issues, but there's still the potential for confusion and different people spelling it in different ways.