Similar to AI PC's right now, very few consumers cared in late 90s. Majority weren't power users creating/editing videos/audio/graphics. Majority of consumers were just consuming and they never had a need to seek out MMX for that, their main consumption bottleneck was likely bandwidth. If they used MMX indirectly in Winamp or DirectX, they probably had no clue.

Today, typical consumers aren't even using a ton of AI or enough to even make them think to buy specialized hardware for it. Maybe that changes but it's the current state.