If you are trying to attract new members it does help to show that anyone joining can expect to be shown how to shoot and to be instructed formally or informally by someone who can demonstrate that they have reached a certain level of competence in their field.
Not fair to name names but I know of three people who have joined our club and stayed as valuable members largely because they felt the clubs they had belonged to in the past did not provide that same opportunity.
On the other hand if the club caters only for good shots and is not interested in developing their own members then why bother with instructors and coaches, I agree.
The licence is a formal qualification issued by a recognised governing body. That gives it some clout. I could write you out a mock MOT certificate for your car but it wouldn't convince many people.