Development cost and low sales. If they spend to much for the R&D and then sold not enough units to recoup the cost then the business would be in the red.

Over the years they developed some pretty special units. Examples are the Extreme Compute Element (NUCs in PCIe form factor) or the Hades Canyon with RXVega GPU and in general the more gaming focused NUCs. I don't think those were sold in high volume numbers.