Most people rejected Jesus during his mortal life - either because they did not believe who he was - but some because they did not want what he offered.
Some of those who did not want what Jesus offered were evil; and lied about Jesus so that people who would want what Jesus offered would be induced to reject it. There are plenty such people around today.
But some who did not want what Jesus offered presumably just did not want it - for whatever reason. As far as I can understand it; Life Eternal is one of loving and creating. It is a life with other people and a life of activity; yet some people dislike other people and would prefer to do nothing.
The popularity of phrases about the post-mortal state such as Rest in Peace, and the echo of this sentiment on gravestone inscriptions, seems to indicate that many people yearn for perpetual sleep, or perhaps a state of almost unconscious bliss (Nirvana); such people do not want the Life Everlasting Jesus describes in the Fourth Gospel - a life of great perceptual and mental enhancements; but instead a life of inactivity.
Many mainstream Christian groups have little to say about the post-mortal state - and indeed they make it sound more like Nirvana than Heaven; but nonetheless the Holy Ghost is active and accessible to everybody, and so people can intuit directly for themselves the nature of Christ's Heaven; and perhaps some don't much like it.
My understanding of the general attitude displayed by Jesus in the Fourth Gospel is that he never expected everybody, or even a majority of people, to choose what he brought us. I think, in the past and in some places, a majority really did want Heaven; but nowadays it seems likely that a majority want Hell or Nirvana.
God cannot have known how many people would want the Heaven he made for us; because we are each different (from eternity) and have unique experiences; and have the reality of free will; so our choice at the point-of-decision cannot be known with certainty.
But I suspect that those who actively opt-in to the Heaven Jesus brought us, will be those who are motivated by a positive desire for loving and creating in participation with our Heavenly Family; and while I certainly am one of them, it would not surprise me if I was in a minority.