There are several hypotheses for why it is the female that provides parental care when only one parent does so

According to parental investment hypothesis, the females show better parental care because of following arguments:
Female invests so much energy, it would be risk for her to abandon her offspring without providing care, since offspring may not survive.

The argument depends on males wasting some of their parental investment on non-relatives, incurring costs for no benefit. This assumes that males do not identify and exclusively aid their own true offspring in a brood, ignoring the others.

Another hypothesis that supports above hypothesis is "The association hypothesis". The argument that supports this hypothesis is that:

Females more likely to be the parent around during egg laying or birth. Males may not be around during this phase. Males are physically separated from progeny and thus less associated with the progeny.