Undecided questions
About love and sex

Love is surely an offspring of sex;
as all well behaved offspring, it eventually gets an autonomous life,
so sometimes 'love' is the main character in a relationship;
of course this is not a general rule, it just sometimes happens;
add to that the difference in sexuality between male and female of our species,
fears, anxiety, lack of attraction for several reasons, not the least unconscious fears of various origin,
and you will end up with quite a variety of behaviour; if that is harsh to you,
just look somewhere else, of course meaning some other woman!

Yes sex is important in love and while sex is an important part of a relationship, in the end it's how you navigate the bad times that really define how strong your love is. Too many people are willing to leave when bad times happen , because it's easy to fix with a legal procedure and piece of paper, and sex is readily available elsewhere. In fact, over time if your relationship is based heavily on sex the boredom factor alone tends to lead people to cheat or split up, because they have no other solid foundation. Some people avoid having sex until they are married because of the fear of unwanted pregnancies or that it is unacceptable in their culture..

It is human nature ,I guess.
Women and men express their love sexually,that is how it is.
It is not the only way they got to express their love,but it happened to be an essential part of the relationship.
If someone tries to avoid it ,it is because they are not sure ,whether it is love or not and they don't want to get hurt ,because sexual intimiacy leads to attachment and if the relationship will be short-lived, they want to avoid the consequences of having to split after such an initmate relationship, it could be very hurting.
Sexual relations could also become an addiction and someone who is not sure again of his love or doesn't really trust the partner enough ,will avoid getting in such a relation ,where there is dependency and one of the partners might abuse the other and control them through using the partner's constant need of such a relation.
Nowadays many relations are on and off and people don't feel very secure to trust the other.
Unless the couple is just interested in casual sex ,one night stands or an open relationship ,then they will avoid getting intimite until there is enough trust in the other person.

Another point is that men are said to like the chase and they might get bored soon ,if the girl had sex with them earlier in the relationship or possibly think she is an easy girl.So girls specially tend to be more cautious and many times are adviced to postpone sex when getting involved in a relationship.