My guess is that they don't give it much thought. Many of them have accumulated a lot of Bitcoin for a long time, notice that few of them participate in signature campaigns and 90% or more of what they write is in the WO thread, so I don't think they give it more importance than clicking for a like on Instagram or Facebook.
You are probably right, so maybe those who are annoyed with all those merit farming account should raise awaraness inside WO thread (if it hasn't been done already) so maybe people will stop meriting them. Giving merit in WO should be equaled to giving merit for a bounty report 
Not all WO posts are equal (some are actually great), unlike bounty reports. And after that, if the behavior isn't stopped perhaps DT members can come up with a plan of action--or not.
I don't know what DT members could do to try stop that, without abusing trust system.