But what does SCR latch-up has to do with connecting inputs to the VCC directly?
In normal condition doesn't matter if there is a resistor installed or not. But a good designer have to predict all abnormal situation as well, like:
1. over-voltage to the IC
2. ESD discharge
3. current injection to/from neighboring inputs/ outputs that may get signal from other modules/ boards etc.
4. power pin connection loss
5. strong RF pulse - EMP warfare.
Inputs are not designed to pass much current, so there is "probability" latching-up, and it's easier to install a resistor than estimate 12-20 inputs/outputs interference to each other .