Flying in/out of LBA I get to see the PAPIs on every approach. I was told by my instructor to ignore them as they are set for a glideslope for multi-engined aircraft. If a SEP were to follow them and then have engine failure the glide approach would be so low that you may have trouble reaching the field hence SEP approaches are at a greater angle.
Made sense to me. So now I simple use them to identify the field when entering the zone and to line up for finals.