Defendants are usually on their best behavior in court, as they're trying to make a good impression on the judge/jury. No-one worries about making a good impression on the waitress or the fitting room attendant (unless they're cute).

The waitress is handling my food - and is likely friends with the cooks.

I try to at least make a decent impression.

Yes, but I'm much more concerned with getting the jury to like me so that they don't put me away for 7-10 years than I am with making sure that the waiter doesn't spit in my eggs. The latter is a good reason not to be a jerk. The former is cause to dust off the company manners that my mother beat into me as a child.

alternate viewpoint:
never hire a lawyer who goes into the process classifying client as "criminal"

Good point. Though there are definitely cases where the defendants freely admit they've committed a crime - it's just a matter of degree of punishment.

If you've ever been convicted of a crime, you're a criminal. (Technically, it's a valid label if you've ever committed a crime, but at that point it includes so much of the population as to lose any power of distinction.)

The fact that a client is a criminal has little bearing on whether they are guilty of the specific crime they are currently charged with.