How cruel is purposely stringing along a girl for years and making false promises?

I've heard of sad stories about young girls who were between ages 18-20's when they met the boyfriend. The guy fills their young minds with promises of commitment and marriage in the near future, makes the girl move in with him and continues with those promises.

By the time the girl wants the relationship to process to marriage as he promised, he makes excuses. The girl is now a woman in her mid-late 20's or even early 30's by then. He drained her all of her youthful years... years she'll never get back.

How cruel is that?
How cruel is purposely stringing along a girl for years and making false promises?
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