In Udupi cuisine, dals are not extensively used in sambars, but are used in making chutneys. Horse gram chutney, toor dal chutney to name a few(actually, I only know these two :) ).
Horse gram is claimed to make the bones strong(source - Veena :D). It is used in rasams, uslis(stir fry), chutneys, idli. You need an acquired taste to enjoy this. I didn’t like hurali(horse gram) as much when I was a kid, but nowadays I am a big fan.