I'm guessing it's because Krivsky has told them no enough times for them to finally believe it, but I could be wrong:
Not long ago, the Astros would have jumped at the chance to acquire Reds left fielder Adam Dunn, who grew up outside of Houston.
The Astros, while intent on adding a slugger, do not consider Dunn an appealing trade option, a major-league source says.
Dunn led the majors with 194 strikeouts last season. He has hit 40 or more homers in each of the past three seasons, but his on-base/slugging percentage has declined in each of the last two. His defense and conditioning are further concerns, and the long-term presence of Lance Berkman would prevent the Astros from moving Dunn to first base.
I said it the other day, but I really don't think the Reds are going to move Dunn. I did back when the season ended, but I've since changed my mind. I'm going to give Krivsky enough credit and assume he realizes that the Reds would be taking a huge offensive hit if they deal Dunn. I really think the only way they could replace the lost offense would be if they could go out and get Carlos Lee, and I have a hard time seeing that happening.
Rosenthal also had this about Marcus Giles:
The Indians are another possible suitor for Marcus. The Reds could acquire him and move second baseman Brandon Phillips to shortstop. The Cardinals and Giants are among the other clubs with openings at second.
Giles would be one of the biggest free agent acquisitions in Reds history, [edited: he's not a free agent, I'm an idiot - he'd still be one of the bigger trade acquisitions in Reds history though] and more importantly he would make a lot of sense for the Reds. I hope that Krivsky will at least explore the possibility.