It would probably be more precise to say that it was true for cart-based consoles: likely due to backwards compatibility with the GB port Nintendo supported enhancement carts until the DS (though by then it’d become very uncommon).
And the N64 technically supported cart enhancements though only a small handful of japanese games used it (Morita Shogi 64 had a modem and rj11 adapter in the cart… and RCEs so you can use it as a homebrew vector).
Once cart were replaced with optical drives there was no way to have anything but data shipped with the game, so enhancements was limited to whatever the console designer had specced expansion slots or even just controller ports for.
Then again, as hardware became more complex an expensive, the ROI on bespoke chips got lower and lower. SETA released 3 single-game chips, there’s no way that’s justifiable nowadays.
