Situations where a scan with advanced tuning options is useful:

From time to time there are new channels added, other channels removed or renamed on your preferred satellite (or other DVB modes like DVB-C or DVB-T as the advanced tuning-options are also available there).
Perhaps you have accidentally deleted a channel that you want to back in the channel list.
Now instead of making a time-consuming full scan you can manually scan to just a single transponder or even a single frequency with specified parameters.
Another circumstance can be channels with non-standard tuning-parameters that are not found during a normal channel-scan.
Even LNBs with non-standard local oscillator frequencies (LOF) are correctly tunable here.