You ask...
How many more people does it take to have their door explode and be hurt, for Whirlpool to do something about it?
Well in your instance - from what you say - nobody was hurt - so the question - how many more? is unanswerable.
I'm sure the manufacturer makes allowance for injuries caused by dangerous or defective products and has liability insurance.
You may have an obligation to inform the manufacturer I think - but they likely know about it already. And the outer glass panel will surely offer protection from flying shards.
As for why it happened I guess that the heat of the oven caused the glass to expand and the expansion caused so much stress in the material that it fractured.
Replacement glass can be bought from online stores - YouTube has videos of how to fit the new glass.
https://www.youtube.com/watch?v=skpONuI6N7Q
Good Luck...
March 2017