People lower compression, to increase the margin of error. To be able to run more boost, without the added risk, of the added heat from the compressed air, on top of higher level of heat within the combustion chamber because of the higher static compression. Low compression with massive amount of boost will yield a sluggish low end, but will support huge amounts of power on pump gas and alot more torque from running alot of boost. The most critical aspect, in deciding wether to run higher or lower compression, is the octane rating of the fuel being used.

Low compression you can run massive amounts of boost on pump gas, have less thermal stress on the engine, but at the expense of maxxing out most compressors on the pump gas level. A high compression engine runs less boost on pump gas, but has the ability to make a greater amount of power on race gas.