Not everyone wants to do it. Many folks who say they want to do it won't follow through if invited.
I started in 02, when a bunch of folks I know put together a group to go jump.
That was actually the 2nd year it happened, I didn't hear about the first until after it happened.
This turned into an annual thing.
This should have been the 20th annual, but it didn't happen.
A good friend of mine and I were the only two people who kept at it and got licensed. He was in on the first one, but didn't really pursue it until the year I started. I landed after the first one, said "I am SO doing that again!!!"
We're both still jumping.
After we got licensed and became members of the club DZ we were at, the guy who started it all kind of 'handed it off' to us, so we were organizing this group every year.
Every year, we'd set the date and get the word out. We'd get anywhere between 30-50 people who would swear up and down that they wanted to do it, and would sign up.
The number that actually followed through was anywhere between 15 and 3. Yes, the smallest year was 3.
That's how it goes.
As something of a side note, my buddy ended up getting his TI rating. Every so often, we'd be talking to someone and the fact that we jump would come up. Almost everyone would say something like "Oh, I've always wanted to do that someday", and my buddy would say "Well, I'm a tandem instructor. We can go out to the DZ this weekend and I'll take you". Maybe one or two said 'yes'. Most folks said something along the lines of "No, I meant I want to do it someday, not this weekend."
Don't stop inviting people, but don't expect more than a handful to say yes.