guesting kills local ppl.
It appears that English is not your first language so I hope I am interpreting things as you intended.
1) Guests do in fact get chests from completing the events. Same as you would. This feature was supposed to allow friends to guest and play with each other and still get the rewards.
2) Kicking those guests who are there to play with friends would unfairly split their group. This is not an optimal solution.
My theory is that there should just be a hard limit in place on each map that says 75% of the slots are for home players and the last 25% can be guests. If home players get kicked into overflow (even with the 75% availability), then home players should get priority over the guests in the overflow.
However, ArenaNet has recently announced that they would be changing how the loot is awarded. It will no longer be “chest per character per boss” it will now be “chest per account per boss” as detailed here: https://forum-en.gw2archive.eu/forum/info/news/Upcoming-mega-boss-chest-change
This should alleviate some people farming it for loot.