To have the block button forces safer play. In most other games, you can be risky if you feel like the opponent cannot respond, either by forcing a cross-up or a fake cross-up. I.E. Sonicfox's bat uppercut cross-ups, which otherwise are massively unsafe, are made viable due to the difficulty in blocking.
Instead, in MK, the pressure is put on the attacker to ensure their pressure is safe. You can't just elbow charge and hope it connects because it might cross-up. This is what I feel, at least, where as in other games the defender is paying for allowing their opponent in, in this one the attacker is forced to play in a way that makes for smarter approaches.
Keeps people honest, and opens up the window for a more diverse cast where in other games it might not be possible to do the same because it would be too taxing on directional blocks.