I heard someone make the analogy once, in a talk, that if we had a business, we'd advertise it, we'd get people to spread the word, we'd let people know what a fantastic product it was, and how they could benefit from it. Yet that would be only for our material gain.
Yet we have the greatest thing in the world, Islam, and we don't have that same zeal for it. We generally don't talk about it voluntarily to others, we've never really bothered finding out how to/the best way to talk about it, yet this is something that will not bring material gain, but eternal success, not only to us but to those who we share it with and then subsequently accept it :ia:.
My fear, is that those we did not tell clearly, may complain to Allah about us on the day of judgement, that they knew us, but we did not convey Allah's message to them.