What was the incentive for them to move to Jamestown and Plymouth Colony?
Because they came over as large, corporate-sponsored ventures for (at least in the Plymouth case) pre-existing communities in which there already were married and young women, rather than the arrivals coming mainly as part of state-sponsored activities (and state employees are going to be men) or private parties as military muscle, landowners, skilled craftswork, sailors, ect. (Who, at the time, were going to be men), or coming over in drips and dribbles as footloose young men with nothing to lose or hold them back to make a go at it (Who obviously aren't going to have a wife and kids to drag along). Men were also more likely to take the big risk of trying to start a new life in the colonies, while in Spain no matter what you did if you're a young women you can make a safe, tidy living for yourself and have less room to rise up breaking into a new hierarchy if you're in relatively safe, stable Spain.