I am perfectly comfortable with having my children run around in the same streets as people selling drugs or stolen credit card numbers online.
But to address your point less literally - "it might make it easier to catch criminals" is an extraordinarily weak justification for compromising the privacy of BILLIONS of citizens (WhatsApp, sadly, runs most of the personal communications in vast swathes of the world).
And crime is not limited to selling drugs and stealing credit card numbers (which is actually not a thriving business anymore ...), example:
https://www.reuters.com/article/us-britain-abuse-idUSKCN1GO1...
The only exception I can think of is distribution of child porn. Everything else has a massive real world trace that can be used to convict the perps.
What?