I can understand how it would be annoying. I am just finishing my first issue of a new printzine, and it will have no ads or anything. Although a label said if I interview their bands they would purchase fifty copies. I didn't do it just because I felt like ti would be my integrity for sale, and that isn't why I bother making a zine. In the past with a zine I had I would get promos and they were usually crap honestly. Even though I said I was only interested in underground death and black metal I received tons of power/prog metal, noise, ambient, rap-rock and every other piece of commercial garbage imaginable. SOme labels like earache send cds with voiceovers on them that say "you are listening to the new...album" every few minutes making it impossible to enjoy the album.
I don't mind trading zines for tapes but I would only trade for bands I want, not stuff the label wanted me to review. I mean after all, with a zine it is still contributing countless hours to drawing, printing, aligning text, hunting down bands, and then afterward paying to print and send out copies often with less than a dollar made on each issue sold, so receiving underground tapes and cds seems like a fair trade.
Most really great bands/labels wont even bother sending though. I mean so many bands have limited edition vinyl/tape/cds now it is as if a lot of bands barely want anyone listening to them...
Plus I will usually only write reviews or suggest some underground albums. Also I like to do a history of albums that interest me. Like the "history" of Incantation's tribute to the goat or bolt throwers peel sessions. It can sometimes be interesting to study about the history of bands...