Some people want the control without it becoming a full time hobby.
I wanted a NAS. I could do it with Linux and ZFS, rolling my own with full control. However, I didn’t want to sink that much time into it, and figured when something needed to be done, I would have forgotten so much I’d need to relearn over and over again.
Instead I went with a Synology. I get my NAS, I’m in control of my data, I can run some stuff with Docker on it… but I don’t really have to spend any time playing sys admin on my weekends.