Sex is a pre-requisite for dating if you daughter allows it to be.  She needs to learn to say no to men she does not want to have sex with, or does not want to have sex with yet, or she needs to let the men she dates know that she is waiting until marriage.  Many men find a virgin exciting so no one has to do anything.  She may lose some men who are unwilling to wait but God has the right person for her who is willing to wait.
Greater freedom always requires greater fortitude and self control but I would not wish for less freedom.  I have no desire to go back to the ways of the past.  
You are correct that a marriage should not depend on sex always being great or readily available as there are times due to illnesses etc. that spouses male and female go thru periods of impotency.  Hopefully, for most, these times are temporary. 
But that does not mean couples should not enjoy sex to the fullest when they can and people often seek more sex, not less, with age, and especially women do.