Being BT, I also can’t see the reason, why BT would like to marry FFB. Do they really want to have a spouse and in-laws, who hate them?”
That’s a rather harsh statement. I married a BT and am FFB. My father Z”L was a great Talmid Chochom and a Kohein, and he and my mother adored my husband, as do all my siblings. Likewise, my husband’s parents loved me. I do not believe that all BT can necessarily successfully be nis-shadchim with FFBs, but to make a blanket statement that the spouse (????) and in-laws might HATE them? That makes absolutely no sense to me. Any in-law might love or hate their child’s spouse. There are so many factors in play.
As a general observation, I tend to believe that most BT might feel more comfortable with other BT, but that does not mean they should not seek a shidduch with a FFB spouse. It might be a little more difficult for them to FIND that FFB shidduch, as people tend to gravitate towards their religious comfort zone.
I met my husband on my own while at work, and not in a shidduch. Had he been suggested to me by someone, I would have probably not initially thought it a shayach shidduch. He had only been frum for a few years, was not in any type of learning program at that time (for real beginners). But Hashem was my shadchan, and sent the kindest and most ehrliche man I have ever known, into my office on the day we met, and what he lacks in learning (though he loves any and all Divrei Torah), he more than makes up for in being the best role model in the world for our children, and an incomparable baal chessed.