In academic papers, there's two ways of thanking people. The first is to acknowledge their contributions by giving them some form of authorship. This is uncommon, and usually reserved for major contributions, because authorship implies they helped direct the research. Authorship is one of the things people look at when hiring, and again at tenure review.
The second way is a section called `Acknowledgements`. That section is for people who didn't do enough to deserve authorship, but made a contribution to the research none the less. Unless the field work was especially demanding, this is where people who do field work typically get stuck. Examples where field techs wouldn't be put there would be fossil/archaeological digs, studies that involved especially difficult sampling, very long-term work by an individual, and papers where the subject matter is field techniques (etc).
Now. A few years back I helped out some research with an unnamed PI. The work was difficult, but not exceptional. I figured in addition to the money I got for my aid, I'd get an acknowledgement out of it. Today, I saw the publication the research was for finally made it to press, and I open it up to see my name in print (something scientists love seeing).
But my name wasn't there. I scrolled the list - everyone else on my crew was there. Where's me? They didn't include my name anywhere.
I don't need it, but I would have liked to have seen it. And not including someone is one great way to kick a scientist in the face. At best, it means I've just been forgotten, and unappreciated. At worst, I've been outright snubbed. I hope it's the former, but either option isn't good.