Why does preferences file get installed in /usr/local despite setting custom install prefix?

Hi all,

I set a custom install prefix while installing from source. However, the preference file still gets installed to /usr/local, as you can see from the gnuradio-config-info output below.

gnuradio-config-info --print-all
/home/.../envs/uhd-gr-default/
/home/.../envs/uhd-gr-default/etc
/usr/local/etc/gnuradio/conf.d
/home/.../.gnuradio

Why does preferences file get installed in /usr/local despite setting a custom install prefix? And is this expected?

Regards,

Wan L.