RRD Command - Averages?

Why does LibreNMS tell RRD to graph “AVERAGE” values rather than “LAST” values?

For example,
rrdtool graph /tmp/asdf … DEF:outoctets=device1/port-id28176.rrd:OUTOCTETS:AVERAGE DEF:inoctets=device1/port-id28176.rrd:INOCTETS:AVERAGE DEF:outoctets_max=device1/port-id28176.rrd:OUTOCTETS:MAX DEF:inoctets_max=device1/port-id28176.rrd:INOCTETS:MAX …

I would like to keep and be able to graph unsummarized data for 5 years of 1-minute polling. Is there any point in keeping 5 years of “LAST” values, or should I configure the RRA to keep 5 years of “AVERAGE” values with an average step of 1?