Most clubs try different initiatives to do better. Events have wash-up and review discussions afterwards. Many try different advertising strategies, more passionate admonishments for members to be more involved, supportive or more generous.
The most difficult problem lies where you cannot tell which of your initiatives work or otherwise. For example, you might be reaching more potential members, but no new applications. You might increase your efforts in promoting a club event but attendees are down on last year.
Not knowing exactly where your challenges lie is akin to a doctor prescribing an antibiotic when the real issue is that you have a sprained ankle. Or giving you a bandage when you really have influenza.
It's little consolation to your club if at the end of your year you observe "Gee - membership applications are down" if you have no hope of identifying why, other than assumptions. You should, in fact, know why long before you feel the impact.
Here are just some of the ways your website can give you continuous market intelligence about your club that's hard to get any other way: