Maxperson
Morkus from Orkus
Like a lot of things AD&D, it was pretty schizophrenic.
For example, while you can talk about xp for "tricking" monsters being in the 1e DMG, you also have the training rules. A fighter that didn't fight was actively penalized by being forced to take longer to train and spending far, far more money on training, for example. In 2e, while there were "bonus Xp tables" again, fighters ONLY gained bonus xp for killing stuff.
You focus on tricking monsters, but ignore that it talks about avoiding/disarming traps as well. There are no monsters(typically) involved with traps, and yet the DM is supposed to come up with an encounter level for them in order to assign non-combat XP.
Add to that the published modules of the day, which again, leads to a VERY schizophrenic experience of 1e where the DMG advocates one thing and the modules pretty much entirely ignore the DMG, and it's very easy to see why murderhobo play was pretty common.
Modules are a different beast. In order to appeal to the widest audience, they have to be written murderhobo and then DMs can add or change them to suit other playstyles. It's MUCH harder to do it the other way around.
IOW, if you kill the monster and take the treasure, you are guaranteed a certain xp award. If you trick the monster and steal the treasure, your xp reward will be based entirely on whatever you DM feels like. You tricked them too easily? Oops, sorry, no xp for you. And, frankly, that sort of thing just leads to far too many arguments at the table. So, DM's and players both shied away from it and relied on the codified rules.
There is also, "If you trick it and it was harder to pull off than killing it, more XP for you." And of course the non-combat XP in that statement regarding traps.
And, lastly, we're left with this bit of advice on page 85
IOW, all that stuff that isn't killing and looting is "conducive to non-game boredom".
Not quite. Not going out and looting is "conducive to boredom." That's why there's the whole section on stealing, sneaking, and traps, and why XP was tied to loot many fold more times than killing monsters. He expected people to avoid fighting and dying whenever possible.