The Matrix spec is still in development and E2E has been in progress since the beginning. It is not an "optional addon", it will be part of the core when merged. You're looking at the wrong branch: https://matrix.org/speculator/spec/drafts%2Fe2e/client_serve... is the in-progress spec, and https://matrix.org/jira/browse/SPEC-162 tracks all the progress. Meanwhile, it's even landed on the develop branch of Vector already (at least for the 1:1 ratchet).

Exactly the same what i thought. This would lead to 216 constant packets per second over the 24h

I was checking my Google Activity Report and discovered i can see a complete profile of my movement for the last 3 weeks.

This is nothing i want to be visible to anyone! You can disable it but why was it enabled in the first place?

Personally, I enjoy having a repository of my location history that I can browse easily. Where was I on such and such a date? Easily looked up.

As for the privacy issues, they are real, but my carrier could easily replicate this data if required to anyway. So if it's going to be generated with or without my consent, I may as well have access to my own copy.

For instance, Google Now analyzes it to help provide interesting cards. Lots of people love that.