I have a theory that like many of the issues we have today, the situation of girls not finding a shidduch has always existed to some extent (In the alte heim, if a girl could not afford a dowry, she had very little chance of getting a shidduch. In early 20th century America, it was hard for a frum person to find another frum person to marry.) but now it is more noticeable because the frum population has B”H grown so much over the recent past, so that even if the % has not gotten larger, it translates to a much larger number, a greater critical mass so to speak that requires community attention. Also, the world is a smaller place- so that we are more aware of the problems that exist beyond our small communities. And since unlike past generations where the struggle to just survive and remain frum took up so much effort, now we can “afford” to notice other pressing issues affecting our communities.
