I went on a round of job interviews back in 1989. I registered with an agency who set me up with one or two promising leads, all over the country.
So I got back from one of these after a drive of about 100 miles or so, to find my phone had been ringing off the proverbial hook. The agency had been trying to get hold of me to demand why I had not rung the company straight back to thank them kindly for their time. I replied (quite reasonably, I thought) that for one thing I had thanked them personally at the time, and for another, I had only just got through my front door.
Apparently the agency had contacted the company immediately after my interview had been scheduled to finish, to ask them what they thought of me. Apparently I hadn't come across as "enthusiatic" enough. I explained that I was an engineer, and I had a phlegmatic personality which just does not do fake enthusiasm. I had spent the time pondering what I was hearing, and involving in a dialogue to determine whether I was right for the job. So "enthusiasm" hadn't been my first port of call.
She informed me that unless I shaped up and changed my attitude, they'd be finding me no more interviews to attend. I concurred with their final assessment of the situation and contacted another agency.