If Concern is Gaming then:
Most games... <ahem>... the vast majority of games only use 2 cores, there are some games that can use 3 cores, fewer still that can actually use 4 cores effectively and maybe 2 or 3 games that can actually use more than 4 cores.
1) if all cores are used, they don't get parked. They are only parked if the CPU is not busy and
2) It helps you to save energy. Unused Cores are parked and not used which results in a lower energy consumption.