Ok so there are a lot of questions on the email!

There are two answers:

1. its a technical limitation - it was easier from a coding perspective to generate the output and send as an email than it was to display it on the site. We're working on updating this now
2. ultimately we have a "good faith" dilemma here. For this to work well, we need everyone to submit accurate data. We have some error checking but one of the way we thought about it was by adding a bit of an extra hurdle. The email step provides that

On anonymous - the email is used to send you your results. Your rent data is anonymized and aggregated so that there is no way anyone would ever be able to tell what rent was associated with what user (email or not). The anonymous part is the fact that the rent data is segregated and anonymized so there is no risk of anything ever being shared.

Did that answer your question? Frankly, this is an issue we're working on fixing because a lot of people seem annoyed by the email.