As some girls get older, their vanity grows. They're captivated by their own looks, admire themselves in mirrors and windows, are proud of something they didn't contribute to in any way. They're waiting for their beauty to blossom like roses, to find good husbands at its peak.
Laurie has seen enough of their kind.
Even more did he learn to cherish Beth who doesn't cultivate her looks but her heart. She's kind and gentle, and when the other women lose the fairness of their youth, Beth's heart will still be in bloom, as beautiful as the day he met her.