nier-automata
In NieR: Automata, there are a few machines that I have found that are called apologetic machines. I tried looking on the wiki, but there wasn't much info outside of what I found out by talking to them.
They tell you to avoid the place, and then blow up and give you an item.
Is there a purpose for these machines or a lore behind them? Or are they just there for giving you an item?
There appears to be a total of three title screen backgrounds.
The default title screen looks like this:
If you
achieve ending [B] (complete the game as 9S),
then you will unlock this title screen:
However, once you achieve ending [E]
and choose to delete all save data,
your title screen will change to this one:
From what I have found online, you cannot manually change them and, going down the list, each title screen appears to replace any previous one, which means unlocking the final one will make that your title screen permanently from that point forward.
There are rare fish in some of the fishing areas that can't be found anywhere else. The specific rare fish that I believe the character was talking about in that email would be the Twinfish and Bloatfish, as those can only be found near that character's house.
Other rare fish would be the Basking Shark and Swordfish (and their machine lifeform variants) near the Missile site in the Flooded City, the Coelacanth (and its machine lifeform variant) near the coast in the same area, the Beetle Fish and Arowana Machine in the Oasis, and the Fur Carp and Arapaima on the path to the Ravine.
Those fish can only be found in those specific locations and some of them are fish I've never even seen.
For the full list of fish in the game, here's a link to the wiki.
Best Answer
Without the DLC, that is the extent of the use of these machines. They served no purpose until the release of the 3C3C1D119440927 DLC.
If you have that DLC pack installed, then these machines are replaced by machines that invite you to participate in their arenas. The quest for the DLC will add markers to your map to help you find these locations again, so don't worry about keeping track of where you saw them.