A moment of silence for all of the fictional mothers that had to die in the name of tragic back story and character development.

— @Snape on Mother's Day 2015

This is something my kids have noticed. It seems like every movie we show them: the mother is dead, sick or missing.

• Frozen. The mum's dead.
• Cloudy With A Chance of Meatballs. The mum's dead.
• Finding Nemo. Mum's killed.
• Despicable Me. Mum's dead.
• Lilo & Stitch. Dead mum.
• Big Hero 6. No Mum.
• My Neighbor Totoro. Mum's sick.
• Epic. No mum.
• How to train your dragon. Mum's dead.
• Annie. No mum.
• Harry Potter. Mum's dead.
• Star Wars (a new hope). Mum's dead.
• Star Wars (clone wars) Mum dies. Horribly.
• Bambi. Bye mum.
• Spider man. No mum.
• Batman. Mum killed.
• Superman. Mum exploded.
• The Little Mermaid. Dead mum.
• Aladdin. No mum.
• Beauty and the Beast. Mumless.
• Cinderella. Evil stepmum.
• Enchanted. No mum.
• Ella Enchanted. No mum.
• Snow White. No mum.

So it's a common device... but why?

1. Because it's a horrible thing -- and good writing involves making horrible things happen to adorable characters.
2. Because it removes a safety net from the character: they can never run to their mother for help. (Mums are expected to be awesome)
3. Because it's improper to show an imperfect mother. The dad can be a bad father (who learns) but women have to be perfect. Better dead than imperfect.
4. Because writers don't know how to portray a mother. Writers write based on cliché and trope. There's no trove of mother tropes to fall back on, so it's easiest to remove the mother entirely.

A few rare films where there is a mum:

• Toy Story. There's a mum. (Not for the toys though)
• Tangled. Mum lives. (Not an active character)
• Brave. Mum is a bear. A fantastic mum.
• How to train your dragon 2. <spoiler>Mum was alive all along! (And she is awesome!)</spoiler>