One reason might be they're not getting a diagnosis. When I wasn't recovering from Covid and showing signs of (what I now know to be) ME/CFS, my Dr didn't give me a label. So I hadn't the slightest idea where to look for information*. She was perplexed and told me to increase exercise. Also I was in the fortunate position of having worked with Drs before and had relatives who had experienced medical misadventure, so I didn't have them on a pedestal as a profession.
I was struggling just feeding myself and doing daily activities, while barely managing to get through my job and holding on by my fingernails & her advice was to increase activities?! It was so obviously ludicrous advice combined with her psychologising / dismissing me, that I didn't take her seriously for 1 minute (while of course pretending to take her seriously because of the risks of not being a 'model' patient).
She should have advised me I was way too unwell to be trying to work and needed time off work. The option of just stopping work hadn't crossed my mind for obvious reasons and I was going to a Dr trying to get to the bottom of it so I could work and continue with my life... instead shocked to find all this gaslighting right at my most vulnerable moment. Her dismissal made me feel briefly suicidal. I was so incredibly ill and the one medical person you are supposed to go to for support was fobbing me off.
Luckily I unexpectedly happened to see another Dr who immediately said I was too unwell to be in work & signed me off. The illness got worse over time, I believe it was unfolding, new neurological symptoms began, there were episodes where I believe I came close to death. Would that have happened if I'd stopped work sooner, known about pacing?? I don't know but I suspect not. My sense is that an unfolding disease process was at play. But I am certain if I'd followed the Drs advice re exercise, I might not be around now, or very severely ill. I've no doubt about that.
*Will forever be extremely grateful for all the pwME back in 2020 who started sharing their experiences online with LC patients & advised re pacing / resting etc. as well as explaining the medical context.