I have went through numerous times where the Vcc pin is shorted with the GND pin causing damage to the entire microcontroller, for example, pins 3 and 4 and pins 5 and 6 in the ATmega328P :
Image source: Microchip - ATmega48A/PA/88A/PA/168A/PA/328/P datasheet
Why do the engineers always place the Vcc pin next to the GND pin?
Adjacent pins allow very short paths to the critical bypass capacitor.
You always want the DC voltage between Vdd and GND to be pure DC with no glitches or ripples. Longer paths between bypass capacitor(s) and these pins have inductance - which decreases the bypass capacitor's effectiveness. Current pulled by the processor internal switches on these paths are inherently glitchy, which allows any inductance to cause variations.
You'll notice that another critical pin AREF also has an adjacent GND pin. Same reason - you want voltage between AREF and GND to be un-varying.
If you're planning PCB layouts, add these bypass capacitors first, and put them as close as possible to the chip pins.
Because it minimizes the parasitic inductance of the power supply. Or in other words: It maximizes how quickly the part can draw energy from the power distribution network (the bigger the space between Vcc and GND, the bigger their inductance).
How important minimizing parasitic inductance is, depends on the part. Some heavily switching parts like big FPGAs might need a lot of energy in a very short period of time. Such parts usually have many more such Vcc-GND-pairs.
TLDR: With regards to component package design, there are more important things to consider than whether or not 2 pins will short together during PCB assembly.
I wouldn't say that the VCC and GND pins are almost always next to each other because it really depends on the component, but it really helps with same layer decoupling when they are.
It helps with placement, ensures that you can route healthy current paths, and prevents blocking the fanout of other signals that get stuck between the power/ground pins. That's probably as far as it goes with packages like the ATmega328P if we don't dive into the details of the internal die, but with large BGAs, it's necessary to put VCC and GND next to each other to allow decoupling on the back of the board without forcing the engineer to use very small footprints. For some power supplies, it's about minimising the eddy currents and improving EMI.
"Why do the engineers always place the Vcc pin next to the GND pin?". The target customer for most electronic components would typically be dealing with high volumes and/or high-quality professional assembly where shorting between pins is generally caught in a number of ways. I don't think the risk of shorting pins would be a consideration.
