Essentially, it is due to uneven clamping loads between the cylinder head face and the block deck.

Wet liner engines require each liner to protrude above the deck by a fairly uniform amount, other wise the head will effectively clamp the highest liners, leaving the lower ones unsupported.

Uneven clamping across the head can also cause head gaskets to go. The number of bolts, their placement and loading is dictated by the block design and may be marginal in some applications.

One factor that is often cited but is totally irrelevant is the volume of coolant in the block/head. Cooling capacity is determined by flow rate. The static volume is meaningless!

Plastic water pumps failing, badly designed radiators including plastic parts leaking and causing overheats, inedequate cooling capacity, badly designed or underspecced gaskets of course. Basically most cost or weight saving techniques can speed up the process. Modern engines run very hot generally too so there is little margin for error.

The old BMW M50 straight 6s could go 250k on head gaskets with proper use, the replacement, the later M52 and M54 are nowhere near as good..change the materials a bit, up the running temp and there you go, much shorter life.

The main cause that I have found though is simply going too hard on cold engines, thermal expansion differes between materials of course and can cause leaks, stresses and what have you that over time build to become a problem. Then there is owner neglect, not checking levels, replacing leaky waterpumps or other bits. Or component failures such as thermostats sticking shut or cooling fans not cutting in, stupid owners continuing to drive the car with the temperature right up.

A few cars are just crap and prone to it, Rover K series being one. That was for a few reasons, inadequate rigidity between block and head, low coolant capacity with no low level warning, leaky o rings letting coolant out etc etc. Stretch bolts that were too stretchy is a classic. Head gasket is a 40k mile service item on those POS even with the newer gaskets.

I firmly believe though that 90% of the time, it is down to owners and drivers abuse that kills them..its the weak link if you like between huge compression pressures, high pressure hot water and high pressure hot oil, its a couple of mms thick and expected to perform for many thousands of miles, pays to take care of them!

It's not always a design feature that causes or promotes HG failure. An engine can get through the design and prototype testing regime with flying colours but sometimes the problems start when it's put into production. Mass production techniques for casting, heat treeatment, machining and assembly sometimes struggle to retain the rigour and tolerances that the design engineers desire. In particular with cylinder heads the weak point can be the thickness of the deck ie the flat surface that mates with the gasket. The deck thickness is determined mainly by the casting operation and can sometimes vary. Get it too thin and it's liable to distort and contribute to head gasket failure if the motor is used hard, particularly with aluminium.