They do it because they feel saying "woman" or " lady" would be extending too much respect to a woman.
"Female" is a biological term which can be used for animals or any organism.
"Woman" means female human.
We're talking about a class of men that is largely marginalized, and also quite impressionable even into adulthood, so three things are happening here:
1. They mistakenly believe the label "woman" is a marker of morality, value or respectability. They don't understand that "woman" simply means human female, and is a social classification. They don't know that using biological terms like "female" without a biological context, lets others know they're uneducated.
2. These men from marginalized communities often try to claim whatever power they can. They dont hold socioeconomic power, so language becomes their play of dominance. They insult and denigrate women, and people from other marginalized communities (gay ppl, the disabled etc) to feel a false sense of personal power.
3. They were socialized in communities, or exposed to media, where other men used the term "females". These men are often quite impressionable and undereducated, so theyre not critical about their speech and continue to use that language without introspection.