Well (to be completely honest), they do this in call centers to make the CSR (call center representative) responsible for intentionally bad calls, and they also realize that the most pissed off person will mark everyone down out of spite.
Those surveys tend to fall outside the 95% mark and aren't counted against the CSR. Now if the CSR was getting this EVERY time, then the problem is the CSR (or the skill queue they are put in.)
But the surveys do not replace monitored quality assessments. The survey only proves that you weren't paying attention to the customers needs. (When I worked a queue that was specifically giving people uninformative DMCA notices, I got mostly bad scores, because who would ever consider "you are ruining my business (selling counterfeits)" a good outcome.) What the customer doesn't realize is that those surveys would never ever count.
In the context of FFXIV, a survey for low-level content would have the highest weighting, while the hardest content would would have the lowest weighting, since less people play it. You would have to have a >50% low rating on a Coil run to be blocked from it, where as a >25% low score would be enough to be blocked from low level.
A player who "abuses" the survey system would have their weighting reduced, which in turn would likely result in them being unable to use the DF with that role if it was.
If you mark everyone low, you are marking yourself as low.