because tons and tons of potential solutions exist. At the core of this class of product is a very simple computer that costs next to nothing. FOSS software exists to accomplish the same goal and for minimal cost someone can compete with them.

Synology doesn't really control anything. In the enterprise segment they tend to be tiny little offerings that are on the small end of SMB. Their bigger bulkier enterprise stuff is easily overshadowed by any real enterprise offering from a larger hardware company, though i've seen some exist even in larger orgs but it's not because something else couldn't have done the job.

Anyone starting fresh has to do some work to catch up but it really depends on the use case. Basic NAS/DAS functions are so trivial.