For whoever has, to him more shall be given, and he will have an abundance; but whoever does not have, even what he has shall be taken away from him.
— Matthew 13:12
I think Jesus speaks of two different persons, the one who believes and the one who doesn't. He who believes will be given more, even eternal life and the one who doesn't believe will lose out even on the things he thought he owned.
“Now no one after lighting a lamp covers it over with a container, or puts it under a bed; but he puts it on a lampstand, so that those who come in may see the light. For nothing is hidden that will not become evident, nor anything secret that will not be known and come to light. So take care how you listen; for whoever has, to him more shall be given; and whoever does not have, even what he thinks he has shall be taken away from him.”
— Luke 8:16-18
He that has an open heart for truth will hear, he with a closed heart for truth won't.
Quoting Adam Clarke:
"Therefore speak I to them in parables - On this account, viz. to lead them into a proper knowledge of God. I speak to them in parables, natural representations of spiritual truths, that they may be allured to inquire, and to find out the spirit, which is hidden under the letter; because, seeing the miracles which I have wrought, they see not, i.e. the end for which I have wrought them; and hearing my doctrines, they hear not, so as to profit by what is spoken; neither do they understand, ουδε συνιουσι, they do not lay their hearts to it. Is not this obviously our Lord's meaning? Who can suppose that he would employ his time in speaking enigmatically to them, on purpose that they might not understand what was spoken? Could the God of truth and sincerity act thus? If he had designed to act otherwise, he might have saved his time and labor, and not spoken at all, which would have answered the same end, viz. to leave them in gross ignorance."