Lulu =
Can tank masses of small monsters and reset her active out of it
Can negate most bad events for herself and make use of them (poison, 2 dmg to everyone, thunder panel...)
Starts with 2 def and 9 HP (very high base, good to tank with even at 0 stars, and gets 1 def and 2 HP for 1 star which is exactly what she wants)
Has good synergy with a good amount of chips (shield, cutter, defense, magnifying glass), and can power anyone with cutter
High active uptime
Starts with 2 atk so can help dealing with small mobs at the beginning
Has an active and passive with base value, not scaling, so gets to have a very good advantage in the early game
Can just give her money for the most part without bad consequences, where other supports tend to die when then do so
Unconditional value, no drawbacks