Premarital sex in Islam

I’ve been told that premartial relationships are haram because they
lead to premarital sex, and that makes sense in the old times, when
contraception wasn’t as readily available, but in the modern era,
where condoms are and other contraceptives are easily available, why
are premartial relationships and sex prohibited? The way I see it, as
long as STDs and unplanned pregnancies aren’t an issue, there doesn’t
seem to be a huge problem with either premarital relationships or
premarital sex. Care to explain?
In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

You have been wrongly informed regarding the reason for the
prohibition of pre marital sex. In the past there were effective ways
to avoid pregnancy. The illustrious Fuqaha have even discussed the
laws of Azl( coitus interruptus) in which ejaculation takes place out
of the womb. The prohibition of premarital sex is absolute whether one
falls pregnant or not.
In fact every type of pre marital relationship is regarded as Zina.
This includes talking to ones future spouse through telephone, Skype
or internet chatting.
If potential spouses are convicted of pre marital sex, that is
regarded as fornication and in an Islamic state both will be punished
with 100 lashes. If pre marital sex was permissible, that would lead
to fornication across the board. Two persons who are convicted of
fornication would simply have to say that they are future spouses and
justify their fornication. Taking it a step further, extra marital
affairs too would be permissible as the convicted couple would simply
claim that they are divorcing their marriage partner and would marry
their ‘fiancé/e’.
The prohibition of pre marital sex is to safeguard the chastity,
dignity, and honour of future spouses and especially the girl from
abuse. What would happen if the future spouses engaged in sexual
activity and then one of them have a change of mind not to marry? That
could be devastating especially to a girl who may have sacrificed her
virginity to the person. While we do acknowledge that this could
happen even after marriage, however, there are laws regulating divorce
issues to safeguard one from such injustices. That is not so before
marriage. A woman would be used in the pretext of marriage to fulfill
ones carnal appetite and simply be dumped. In this world of
technological advancements where ones sexual appetite is unlimited,
men conduct themselves like vultures to prey on women and abuse them.
This is a common occurrence.
A women has a natural right of dignity and honor. She should never be
left to be abused. She is not an object to fulfill someone’s passion
and desire. She deserves much more than that. There is much write up
about women serving as prostitutes in dens. They feel no more than
animals and they themselves realize the beauty of Islam’s teachings in
preserving women in Hijab.
A woman in Islam is treasured like a Jewel. She is thus preserved in
her jewel box- her Hijab.
Mufti Ebrahim Desai