Profit would interfere with impartiality. There would be those who would answer the questions during jury selection in a deceitful manner just to get paid for being selected. Lawyers are supposed to be biased in favor of their client, so they get the big bucks to cover the hours, the effort, the knowledge to represent. Judges, in my opinion are paid mostly for the emotional toll it takes to deal every day with the ugly realities of crime.
I was called once for jury duty, but I am a single mother, so they listed me last on the selection list, so I would serve only if they couldn’t agree on a full jury from those ahead of me.
I sat with my daughter for hours through the selection process, and never got called to the stand to face the questions.
My daughter stayed quite well behaved, by the way.