Guild Wars 2

What good does it do? U get only bags and chests from PVP – and magi find wont work when opening them

I think you just answered your own question

So whats th point of having it?

PvP reward bags are the only loot bags that are actually affected by MF.

….
hundreds opened without MF boosts

its best to have a r80 alt you don’t play anymore loaded up with tons of magic find stuff
put all of your pvp chests in the bank and open them on that alt,
ive got tons of ascended stuff this way

MF is supposed to work by the time you acquired it, so unless you have the MF boost by the time you end the match and get the loot bag, i don’t think it’s gonna work if you open a booster later and open the bag.

No, the mf is impotant at opening, not at getting the loot bags. The bag is a simple item that activates a randomfunction taht creates the loot when opening it.
The original idea is from all those bags you can sell, so you couldnt sell your low mf bags.