Most Helpful Guy
While some guys definitely want and enjoy relationships in their 20s, the vast majority of (western society) men aren't looking for a SERIOUS (as in, marriage-potential) relationship until they're around 30.
Let's look at it.
Guys hit puberty in their early teens - but most have zero game, and can't get a girl. Socially, women have all the power in their teens and 20s, because they control access to sex, and sex is a young man's #1 priority - men's sexual peak years are roughly 16-25.
I'm going to say that again, because a lot of women simply don't get this, but SEX is men's #1 priority, while a relationship is somewhere further down the list - maybe #5 or #8, and maybe #37 or #61. For women, RELATIONSHIPS are their #1 priority, while sex is somewhere further down her list. Men and women are DIFFERENT!
So, teen boy goes through Jr High/Middle School, then High School, and then either on to college or into some trade. The college guy typically graduates and then starts he's career, and like the non-college guy, he's starting on the lowest rungs of the ladder. Through his mid-20s, he's clawing his way up, often barely making ends meet and trying to have some occasional fun, but often working long hours, crazy schedules, working weekends, or having to take a second job. Dating during this period is difficult or impossible.
Finally, by his late 20s/early 30s, he'll have usually attained a bit of status, stability, and some financial security. He actually is able to pay his bills and has money left over (more than the cost of a 6-pack of beer, anyway), and so, FINALLY, he feels like he is ready to have a real relationship.
Before that? He knows he has all of these obligations and expectations to deal with, that he has no status or stability, and will have to take crappy jobs, work crappy hours, etc. because he is "low man on the totem pole." He knows none of this is likely to make a girlfriend or wife happy, and he'd rather spend what little free time he has relaxing rather than fighting with an unhappy partner - which is usually the other option.
And it's a rare girl who understands all this and is TRULY prepared to not only tolerate that phase of his career, but to support him (emotionally and otherwise) through it without being overly demanding of his time and attention.