Zardnaar
Legend
I will not stand for this kobold slander.
Kobolds are the most technologically advanced of the so-called monstrous humanoids. They should be cranking out the high-difficulty locks and traps.
Maybe a goblin or orc dungeon should have DC 10 and 15 locks and trap bypass difficulties, but traps and locks are kobolds' thing. They should be creating the hard ones.
And as for the basic question, of whether this stuff should be so hard, a DC 10 lock is close to pointless. Even at level 1, characters will essentially walk straight through them. Lower than DC 10 shouldn't even be a skill check, since making people roll on things you intend for them to succeed on just sets the players up for slapstick and is a waste of everyone's time as a DM (IMO).
So the only place to go is up.
Maybe DC 15 locks should be the standard, but when you're up against the thieves guild or kobolds or -- worst of all -- kobold thieves guilds, DC 20 is appropriate, IMO.
That said, good DMing wouldn't make a lock a fail state for an adventure. There should always be alternatives, whether they're different routes through a dungeon, only putting helpful-but-not-required items in locked chests, scrolls of Knock or -- crazy thought here -- keys.
Even in AD&D orcs were stupid the typical kobold and goblin iirc was as smart as an average human.