Assuming that all relationships take effort and involve some “cost” of time, money, freedom, and emotional energy, the more someone has adjusted to living alone, the more “hope” that person would need to disrupt the status quo. If the people you happen to meet aren’t “worth” the cost – that is, the prospect of putting in all those resources outweighs any benefits one hopes to receive out of the relationship – you’re probably going to be disinterested in pursuing a relationship with that person. I’d further suggest this is particularly applicable to older singles, especially the emotionally healthier ones who have acclimated and adjusted to living life on their own. It’s not that singles get more “selective” as they get older as much as they’ve learned to live a satisfying life on their terms. In which case, older singles require a proportionally greater “hope” for a better future with any given person. It’s much easier to hope when you’re young because you can still dream of possibilities, even if they might never come true, but the longer someone experiences life, the less such dreams of a better life seem plausible.
Rabbi Josh Yuter, “The Four Letter Word Every Single is Really Seeking. Hint: It’s Not ‘Love'”, JDate Blog (20 November 2014) [http://www.jdate.com/blog/2014-11/the-four-letter-word-every-single-is-really-seeking-hint-its-not-love/]