think about it
when you compress a gast say 11:1 you are multiplying pressure 11 times. atmosphereic pressure is about 15psi (a little less) so when you compess it 11:1 you have 161psi pushing out on the gasket and heads and only 15psi pushing back in...
now add some moderately high boost, say another 15psi, now you have 322psi pushing out and still only 15 pushing back in...too much and a blown head gasket is a guarontee.
on top of this all of that air being compessed causes alot of kenetic heat to be consentrated in one area making the temperature peak quickly (which is how diesles run, but we are speaking of a 4strok gasoline engine) this temperature peak causes detonation which we all know is bad unless you plan on running 112 leaded fules.
when you lover that compession to say 8:1, naturally asperated you have 130psi pushing out and 15 pushing in and with that same 15psi you have 260pushing out and 15 pusing in, there is also less of a temperature peak and lower octane can be used or a more advanced timing can be ran.
now with a higher compression you have a greater thermal efficency but every engine has its limit and every fule has its resistance to detonation.