Voxels have been around since the 1980s. The smoothness came from that beautiful CRT and its inability to display crisp images. Normals weren’t really used until early 90s and used heavily by games like Comanche by NovaLogic.

The reason why Minecraft voxels are blocks is because Notch (Markus Persson) famously said he was “Not good at art”. He didn’t implement the triangulation and kept them unit blocks. Games that had voxels AND were triangulated that came before Minecraft were Red Faction, Delta Force, Outcast just to name a few.

The point is, voxels aren’t anything special, no more than a texel, or a vertex, or a splat, a normal, or a uv. It’s just a representation of 3D space (occupied/not occupied) and can just as easily be used for culling as it can for rendering. The Minecraft style because popular because it reminds people of pixels, it reminded people of legos, and Minecraft was so popular

It depends on how the voxels relate to the gameplay.

Regardless of the original intent, in Minecraft the voxel grid itself is a very important aspect of the core gameplay loop. Smoothing the voxel visual representation disguises the boundaries between individual logical voxels and makes certain gameplay elements more difficult or frustrating for the player. When the visuals closely (or exactly) match the underlying voxel grid, it's easy for the player to see which specific voxel is holding back some lava or if they're standing on the voxel they're about to break.

In Minecraft you can, for example, clearly count how many voxels wide something is from a distance, because the voxels are visually obvious.

In Red Faction, you're never concerned with placing or breaking very specific voxels in very specific locations, so it's not an issue.

> it reminded people of legos,

I don't think this should be understated. LEGO are easy and fun to build with and don't require a lot of artistic talent. The same goes for block-based games like Minecraft.