They breed an unnecessary sense of intra-group competition.
So let's look at the reasons a person might feel obligated to link the damage meter in party chat:
They were asked to do so by someone who doesn't have Recount installed, but would like to know how they are doing. In this case, I usually just whisper the numbers to that specific individual.
They were topping the chart, and wanted everyone to know it.
They want to point out someone's perceived sub-par performance to the group.
They are the tank and want to shame the DPS by notifying them that the tank is outperforming them.
They suffer from muscle spasms, and accidentally clicked the wrong button.
Of those five reasons, one is justifiable, one is improbable, and the other three mean you are a prick.
The first time somebody links Recount in chat, the group dynamic instantly changes. Suddenly it's on. The game condenses down to a single gnawing imperative: I must lead that meter. Whoever is last on the list instantly feels terrible. They may not have anywhere near the gear they need to outperform the other two DPS members of the party, but they feel bad about it just the same, because if you linked, you clearly want them to know how badly they're doing. The person topping the group feels good about themselves, but might also begin to resent the underperforming members of the group, feeling that they aren't pulling their weight. The group atmosphere goes, in one fell swoop, from cooperative to toxic.
What was the point of linking it? The answer, of course, is my fourth reason for hating damage meters: