Apparently it's not a bug it was intentional to have items respawn, unique or not. Dead Island did it and people criticized dead island for it. Now Fallout 4 is doing it.
To be fair to Dead Island, it made no difference whatsoever that the items respawned when you returned to an area.
Any weapons that were out in an area outside of a box were purposefully low-quality, regardless of level. The best items still came from crafting, quest rewards and occasionally chests.
The fact that fruit/cola reappeared wasn't an issue in anyway at all, because there was so much of it in the first place that it would make no difference if you drank it all first time you came through, and even if you had, there were vending machines that would give you infinite cola, for like $2.
And as for the likes of Alcohol, there was crap loads of that too.
The only really annoying thing about areas reloading completely in Dead Island, was that all the enemies also respawned, even if you went into one of the mini-dungeons in the area (like an apartment/cave). And outside some of those dungeons were a lot of enemies, including strong specials, who you had to defeat in order to get in, and then the moment you get out you had to fight them once again, this time without any chance to plan your attack.
Are there any benefits to using pipe weapons over modern profiles such as the Combat Rifle/10mm Pistol and such?
They happen to be, if not are, the most customisable weaponry in the game.
If there's any sort of gun you do want to convert from a pistol to a sniper, then it's those.
Only thing to note is there are two types of pipe-gun, bolt-action, and semi-automatic/automitc (depending on reciever used, I think).
Despite both being pipe-guns, I don't believe you can take parts from the bolt-action guns and put them on the semi-automatic/automatic guns. I may be wrong however.
Also, if you get the Scrapper perk (think that is its name), which allows you to get more valuable materials from scrapped items, then pipe guns become a really good source of screws.
A fully default pipe-pistol will weigh about 2.3, and you get 1-2 screws from it.
Whereas a Desk Fan and any other large object that provides screws, weighs 3-5, and gives 2 screws.
So, they're a little bit better to collect for screws, provided you watch their weight (since it can vary), and they're more common than fans are.