I'm not sure why this is so surprising. The job requires hard working, dependable, passionate, adaptable people willing to get up well before the butt crack of dawn 5-7 days a week definitely inclusive of weekends in all weather conditions. It is also unlikely that you will be year-round, which makes it unlikely that you'll receive full benefits. The pay, while pitifully low before and immediately after the GFC, has increased rapidly this decade, but only to "halfway respectable." Fact is, the job at the experienced level is every bit as nuanced and challenging as other skilled trades (plumbing, carpentry, electrical), but the pay still lags those careers. It is on par with fast food worker, I know this because we've lost decent people to Wendy's FFS. Greenkeeping tends to be lumped in with other landscape trades (one of the lowest paid industries) when it comes to compensation analysis, when it really needs to be off on its own.
It is certainly true that there is no shortage of applicants for head superintendent jobs. The problem there is, a lot of these guys end up being the superintendent plus the spray tech plus the mechanic, plus the irrigation tech. At a very high-end place those would all be separate positions. Meanwhile, the shortage of assistants is acute, and when those guys get hired, they end up doing far less leadership related tasks because they become the mechanic/spray tech/irrigation tech etc. So those in leadership get spread very thin, because the likelihood of walking into a situation where all those tech positions are filled is remote. So while salaries for superintendents look pretty decent, it's a decent salary for about double the work that would be reasonable. This also causes training and development to be lax, as the superintendent and his assistant(s) are often bogged down with daily labor tasks instead of training/mentoring junior crew members. Still it's a career where those who make it to the head spot will have a "get 'er done, whatever it takes" mentality, so the system sustains itself...for now. Meanwhile, the guys I know that have left the industry have never looked healthier.
But by far the hardest position to fill on the golf course is that of mechanic or equipment manager. Specifically a guy who's a good wrench who also gives a shit about quality and height of cut. We have not had a good one in 3-4 seasons now with no end in sight.