Seemed like a simple enough question.
There are lots of ways to draw people in: Extra recruiters; extra advertising; extra pay; extra bonuses; extra education assistance; upgraded living standards at military bases; more flexibility with medical standards, legal standards, intelligence/educational standards, and physical strength standards; more flexibility for prior service folks who want to re-join, etc, etc.
And there are also a bunch of ways to help retain the people we already have -- good retention can help counter-balance soft recruiting results.
I wouldn't say "people aren't volunteering." Even with our extremely tough entrance requirements, the Navy and Air Force are at or over 100%, while the Army and USMC are still recruiting between 80% and 100% of their goal. And there are a hundred ways to open the spigot a little wider if we want to.
That's what I thought, but then I remembered...there's no simple question or answer on an anonymous forum, especially this one...