Because the Learn/Lesson combo meant a lot of options in the set would inherently be two-for-one cards, the set's designers designed most of the Lesson and Learn cards to be weaker than their non-Lesson alternatives as a way to balance the mechanic
For the low, low price of one mana, you get to do any number of cool things, whether its someone else taking out the creature or planeswalker or you doing it yourself
You can expect a more substantial opening experience with more packs to rip and a better overall value proposition for building your collection
Trap Cards cannot be activated
In some scenarios, its also advisable to turn monsters into Spell Cards as the cost of an effect
These cards would normally loose much of their value in the late game, but in this deck they become part of a land ramp and recursion engine that continues throughout the game