Yes - for a lot of reasons.
To start with, your boss today may not be your boss tomorrow. Without a union contract, you have no guarantee that your wages and working conditions will not be undercut by a new boss or, for that matter, by a new owner.
Union’s can provide dignity in the workplace by ensuring that the employee-employer relationship is not controlled by just one party. The best strength workers can have is the strength they lend each other. If your boss genuinely likes you now, they will respect your right to choose a union. This choice will not damage a positive relationship but will in fact strengthen it.