Because it's ambiguous!
Does it mean:
"Do not test the LORD! To be clear: By 'test,' I mean ONLY doing that thing you did at Massah!"
OR
""Do not test the LORD in the manner in which you tested Him at Massah! Other tests - differing from the test at Massah - are perfectly acceptable, however."
The problem with relying upon scripture which is not susceptible to Q&A! The problem with not being able to ask "Wait a minute! What exactly do you mean by that?"
Regards,
Because it's ambiguous!
Oh?
Do not makeup your face as you did at your friends house.
Ambiguous or not?