Answer:
high survival rates of offspring and the cost of parental care
Step-by-step explanation:
Animals must optimize the energy invested in growing, surviving, reproducing, and leaving fertile offspring. They must ensure the perpetuity of the species. The best manner of doing it is by reaching sexual maturity, mating, and leaving progeny that also reaches their fertile age. So sometimes, they need to "decide" or "choose" where to invest more energy.
Those that "decide" to take care of their offspring invest too much energy in doing it. Parents must feed them, an activity that requires most of their energy to produce food or look for it. They must protect their progeny from potential opportunistic predators, so they need to be near the whole time. They need to teach behaviors and habits. And so many other things that require energy investment.
So, where do parents take all this energy from? The energy that is usually destined for survival and mating activities, is now destined for parenting. Often, parents can not feed properly because they can not leave their offspring alone. They face predators putting themselves in danger of being hurt. They can not mate even if they are in the reproductive season.
This is the Cost-benefits energetic trade-off.
Which is the benefit? To ensure the progeny survival, to make them reach their sexual maturity, and to reproduce too. They do it to ensure the perpetuity of the species.
So these species "choose" to have reduced offspring and to take care of them. Many other species "choose" to have many descendants and to avoid parental care. They invest their energy in surviving and reproducing.