A suit would be overkill here in the South. Most people would sweat through a white shirt in no time and then they're no better off than wearing a ratty shirt. Examiners know you are nervous without seeing your pitstains. That said, I always wore a shirt and tie to my rides. Now I have to wear a tie when I'm flying so I look at it as preparation.

I always wanted to see my student wearing slacks, decent shoes and at least a polo on their checkrides. If being a professional pilot is your goal, dress for the job. Doesn't mean you need a monkey suit, just use some common sense.