Any time my adventurer heroically kills an enemy in battle - SP and EXP should be earned, since skill and experience are improved.

Side quests should provide the regular amount of SP for killing the enemies just as if I had killed a wandering marmot.

The lack of SP/EXP earned actually encourages bad gameplay. If you take a lower ranked quest when you have a higher ranked character - the system encourages you to switch to your highest ranked class and one shot everyone in sight - and victory! The quest reward is yours, and it took less than 60 seconds.

If SP/EXP was earned, I would at least switch to a rank appropriate class so that I would earn SP/EXP as I went on the lower ranked quests.