Sheikh Muhammad taqi ud Deen hilaale may Allah have mercy on him narrates on some accounts he saw in Europe:
“From that which is strange I have come across regarding some of the affairs of the soon-to-wed couple is that a man will propose to a woman and so they agree upon marriage [some time in the future]; so they remain living together for a long period of time in a lovey-dovey relationship, and as we have said, complete mixing and mingling just like as if they were married. Thereafter the nikkah is contracted and they’re married together…but not long goes by except their intimate relationship begins to deteriorate, then rifts and problems start to occur, followed by separation.
And from one of the strange affairs I have heard [from a city in Germany] is that a soon-to-wed couple remained together for 20 years in complete harmony and cohesion, then they got married, but no sooner did they get married except after one year they got divorced bearing in mind that even in that year they were married, there were arguments and fights between them. I therefore asked what the underlying reason was for all that happening amongst the soon-to-wed couples and it was told to me that as long as the man and women remain together [before marriage], each one of them would hide their true nature in front of the other and assume/adopt characteristics other than their real characteristics as a way to sweet-talk and flatter their companion [soon-to-wed mate]. All this is done out of fear that one may bore out the other one which will thus lead to the annulment of the real proposal of marriage. Thereafter, as soon as the nikkah is contracted and all that love flattery is gone, and the hidden/secret affairs and habits are brought to true light, disagreement and clash start to follow suit, then argument and fighting…and then divorce.
And by this you [should] know that the speech of some of the gullible and inexperienced Europeans which approve of this free mixing and mingling among the soon-to-wed couple before marriage, along with being in private with her, living with her, with their claim that they must do all this in order for each of them to learn of the true inner nature of the other [in order for agreement to occur] and that love is the basis of a happy marriage, all this is falsehood and decorated lies. This is because there is no way for the soon-to-wed couple to know of the true nature of each other except after the formality is dropped, and this only happens after marriage. Also, the couple is not safe from falling into haram interaction/intercourse and its severe consequences that come sooner or later. And this is why Allah has forbidden [through the prophet’s speech] seclusion with the non-mahram as comes in the hadith of the prophet صلى الله عليه وسلم that he said: no man or woman is in seclusion with each other [non mahram] except that shaitan is the third among them. The prophet صلى الله عليه وسلم also forbid entering upon the مغيبات [those women whose husbands are absent], and he was also asked about الحمو [the brother to his sister in law] and if it is permissible for the brother to enter upon his brother’s wife [his sister in law], and he said “the brother in law is death” intending by it that the brother entering upon his sister in law in seclusion is worse than entering upon other than her from the محرمات [those women who is not allowed to enter upon in seclusion]. And the prophet صلى الله عليه وسلم also forbid the woman from travelling without her husband or mahram [guardian who she is not allowed to get married to], all of this is in preservation of her honor, lineage, and deen, being in harmony, preserving the rights of kinship, etc…As for when you want to marry, it is allowed for you to look at the one you intend to marry without being in seclusion with her.”
Side note: The one who marries with the blessing of Allah and he doesn’t become acquainted with his wife except after marriage, there will be more lasting intimacy and happiness after.