I've gone on field trips, been in classes, and been in meetings with 'terps and their deaf clients; their roles were very different. The field trip, visiting CSUN for a day through a JC, let the 'terps be more relaxed, and easily shift between friend and interpreter. One of the interpreters had actually been a student at CSUN, and when not interpreting, could add information she had and even helped the tour guide when she couldn't answer a few questions. Later, when we all had lunch together, again, the 'terps could be ppl, not just 'terps. In classes, the terps are usually more reserved, though it depends on the 'terp/deafie relationship. Most may chat a lil b4 class, and then just 'terp, nothing more. In the meetings, in was all business, even before the meeting started.
I know I've had very lil experience with 'terps, BUT becuz I am not yet a 'terp, I'm not sure I will ever be, (I'm much more interested in teaching), many deafies will talk to me about their opinions. I don't mean this offensively, but I had noticed the more educated a deafie is, the more they seem to like 'terps, and the more they use them. This could be becuz of more experiencing using them, a better grasp of English, and a better understanding of the role of a 'terp. Also, when a deafie is uneducated, and doesn't have great grammar in ASL or English, it makes them very difficult to be interpreted to/interpreted.
I don't believe 'terps, other than maybe a few CODAs, go into it for the money. To get good money, you have to be a good 'terp, and that take a lot of time, not only in school but also in the deaf community. You have to be willing to be wrong and be corrected, and know that there is always someone who could do your job better than you. A 'terp teacher of mine once said, "I've been doing this job 25 years, and here's what I have figured out. Interpreting is 10% skill, and 90% guessing." Realize that simulataneous interpreting requires you to be saying one message, while converting another message in your head, while receiving a third message. This is NOT easy!