Kernel Configuration for acpid Issue

I’ve installed acpid on my system some time ago (Gentoo package: sys-power/acpid. However each time I tried to start it it complained:

acpid: can't open /proc/acpi/event: No such file or directory

Apparently acpid requires you to enable ACPI_PROC_EVENT, which in it’s labels states “Deprecated /proc/acpi/event support”. I really wonder why such tool only support the deprecated way to receive the ACPI events.