Bitcoin mixers and anonymizing services just gives you the same anonymity that cash gives you. When you draw cash at a ATM and you spend it somewhere it can be traced via
serial numbers etc... but it's cumbersome and most people would not go through the trouble to do that, to know what you spending patterns are or what you do with your money.
When you use these services, you just add a extra level of "security" to your financial matters to protect your finances from marketing companies and and online thief's.
Why would you allow EVERYONE to know how much money you have? It will only paint a target on your back for people who would say... "abduct" your kids and use them
for ransom or break into your house to get to your private keys...
Everyone using these services are not criminals... they just need to protect themselves and their family and their financial privacy.
These features are not built into Bitcoin... so people use these services for that option.