Sure, the data is obviously biased, but that doesn't make it useless. Can we say definitively that the majority of players want a parser? No. However, there have been a lot of discussions on the forums about parsers and there is a large vocal userbase who cries out against it. It is interesting to see that in sheer numbers on this community, the number of players who wants a parser is larger than not. This information could help Square read the previous data from other threads on the subject. It also could simply show Square that there is likely a significant interest for a parser. In other words, no it gives no definitive answers, but it does give information - which is still useful.
Why would you need to have it calculated this often? These calculations are already taking place. The server knows what ilvl we are, what damage we are doing etc. I cannot imagine this being a heavy load on the server - but they could simply have a rolling average calculated in a daily basis, during off-peak times.
I dislike your analogy, because the main reason a parser is useful, is that you are working together as a team to overcome something. In virtually every other team-based environment, performance metrics are monitored and posted. For example, in hockey games, your shots on net, saves, hits, goals, points, time on ice, time on offensive, +/- (etc.) are all recorded and posted for you to see. In a work environment, your performance metrics are undoubtedly recorded (i.e. sales numbers, revenue, expenses, clients, satisfaction rate etc.). In these situations, it is important to have these metrics visible by all for two major reasons. First, your performance often affects your team, and thus it is important to your teammates to know your strengths/weaknesses, where you can improve etc. Second, having this information sparks competition, which is an excellent motivator to improve.
In a game like this, where everyone is working towards a common goal, and there is no parser present. It provides a system which does not promote accountability, cooperation, nor competition. It is in everyone's best interest to let their teammates carry them, so they can receive maximum reward, with minimal effort. This is a well studied principal of human behaviour, and is pretty much the cornerstone of our economy.
I get that you may feel uncomfortable being held accountable, but equally so many people feel that players who are not held accountable distract from their enjoyment of the game as well.