For a couple who does not have a financial backup, having a kid is like adding more to the burden. For a woman who has recently got a big hike and promotion, it is not the right time to have a kid. For someone who has to leave for abroad, leaving the partner with a newborn child does not seem okay, so pregnancy can be delayed. For someone who is physically not healthy to bear a child, pregnancy can be put on hold. Also, for someone who is mentally not prepared to mother or father a child, pregnancy should not be considered.
Elder ones may scorn on these statements, as they feel when a child is born a house sparkles with its smile, cries and antics. But honestly, that does not address any of the reasons mentioned above.