Switches do fail. Also if they use internal springs and they wear out, the can have momentary interrupts. Also putting switches on the outside of the rocket can be dubious as well. If the rockets hits itself during deployment, it is possible, though unlikely, to turn a switch off.
ALL FUD!
I hope to fly a rocket enough times to suffer a switch failure due to wear.
I use "inverted V" contact types with a long wiping area so they don't suffer from momentary intermittent.
I also use redundant contacts on the power so they have less of possibility of intermittent power issues...these switches are 4PDT....the power switch in the photo uses all four contact sets to switch altimeter power. Now that we put trackers in a rocket, they typically have two sets for the altimeter and two for the tracker.
BRIEF (vibrations caused) intermittent interruptions DO NOT MATTER - altimeters have input caps that will ride through vibrations and pyro's will still fire.
Lastly, the switches DO NOT protrude outside the body so the possibility of being deactivated due to contact is very, very low.
Again - we as a team ALL do this and have suffered zero problems across hundreds of flights.
Now -- go back to my story about the found rocket:
Substitute who found the rocket to an innocent bystander unfamiliar with rockets - such as your landowner, his children, a sheriff, etc..
Have an bad outcome from their encounter and imagine the results.....Injury? Loss of a flying field? Worse.....
Make you rocket friendly to non-rocket people.
It's not hard. It's reliable. And just might save your bacon......