Skills have different ways of using them. Some provide you with remembering information. Others are understanding the information in front of you. And others are using the information.
Arcana - Knowledge, I remember that demons often have resistances to Fire and Poison.
Arcana - Analysis, This demon has immunity to Fire and Poison.
Arcana - Use, Activate this magic device to summon a Gem Immune demon.
What other ways have you guys noticed we use skills and what skills do you think are missing in 5e?