Why is the button to open a microwave door always hard to push?

Every microwave I've encountered always has the same feature - an unusually resistant "open microwave door" button.

Why is the button to open a microwave door always more resistant than buttons on other household appliances?

By resistant I mean you have to use more force to push it open.

Any ideas?

Edit based on answers: As of yet, the answers (especially regarding safety) are unsatisfactory because I see the safety interlock mechanisms can be operated without a resistant button and still maintain the safe level of safety. See Miele Touch2Open feature. Why don't more microwaves employ this feature or at least a regular button? Price cannot surely be such a factor since a regular button would be just as cheap.