My hypothesis as to why this is relates to how products over time seem to all converge on inoffensive sensibility and mediocre homogeneity.

The more mass-produced something is or generalized use-case something has, the more important it is for the item to meet every single need. Of course, one of those needs is that the physical appearance of the item needs to match or blend in with the aesthetic of its final location. Not all older, crafted pieces match, and to choose one commits you a particular style. Once you’ve decided on that, the cost to change is significant.

So how do you meet all needs? Design something inoffensive, bland, and sensible.