I don't know. I have another customer who's also against them and also won't give a coherent reason other than "I just don't like them". How do they know they don't like them, not having used them? But, even when asked directly, all I get is evasion.
Sometimes people feel a certain way about something that they know is indefensible and so don't even want to start any conversation about it. Religious and political positions are often that way.
Having been using/installing them for years, the only reason I can think of that even approaches a valid concern is that they're not forgiving. Unlike wood screws, machine screws need to line up just right, especially with relatively soft metals like brass, or you run the risk of cross-threading the insert. Recovering from that is less than fun. Thing is, you'd have to be snot-slingin' drunk/stoned to miss the feel of that happening, so the risk is pretty low.