This is my case. Save for the odd accident every few months/years, I´d never experienced bedwetting while growing up... but then one morning when I was 30 years old I woke up to a completely soaked bed. My ex-gf was sleeping next to me, so it was even more embarrassing and disconcerting. Still I took it as a fluke and let it slide, but it happened again two weeks later, and then again another two weeks later, so I went to see the doctor.
Of course, the urologist´s first thought was that I could have prostate issues, but luckily it wasn´t my prostate. He asked me to take the conventional measures like cutting fluids 1 hour before bedtime, reducing my caffeine/coke/alcohol intake, using the toilet twice before hopping in bed... but still the intervals between accidents started to reduce more and more rather quickly and all of a sudden it was a nightly issue.
Encouraged by my dr and my ex, I started to use a bedwetting alarm, thinking that I could re-train myself... but the darned thing just kept waking me up 2, 3, 4, 5 times on the same night!!! And to make things worse, by the time I woke up my bladder was already empty and I´d have to change my undies and pjs, and the bedsheets too. That´s been the most frustrating period of my adult life. I threw that instrument of torture away and then my ex suggested I could try "some sort of protection" to which I agreed almost too eagerly because not only I´ve loved diapers all my life, but also because I couldn´t take all that extra laundry anymore.
At the same time I was still undergoing many painful and awkward tests to find the cause of my bedwetting, but they never found any underlying illness... then I recalled a painful rock-climbing accident I´d had some months earlier and that´s when they started to consider nerve damage as the actual cause. Indeed it turns out that when I´m sleeping there´s absolutely no connection between my brain and my sphyncter muscles, and that´s why I could no longer get up to use the toilet like I had done before and that´s why no matter how loud the alarm sounds, my bladder is just going to empty itself if I sleep more than 30 minutes. My doctor suggested some medicines to stop my bladder from working at night but I rejected them because I had read about the side effects -and also because I was somewhat happy to have a legitimate reason to wear diapers, even if it was only for sleeping.
But then I started to crave my night diapers more and more until I started using them for daytime as well... and here I am almost 6 years later happily wearing diapers to bed every single night for bedwetting, and also diapered 24/7 for almost 3 years because diapers are the best underwear ever!