From what I've seen, and from comments I've gleaned online, it comes down to the fact that there are three subtypes of DM's out there (among many).
Ones that hate players getting anything, lol, or seem to, and are quite happy that magic items are not "required" (supposedly).
Ones that are very conservative about magic items, thinking they need to be rare or uncommonly seen in games.
Ones that aren't really sure how to incorporate magic items in their games, as the DMG guidelines don't really say "ok at level Y, players should have X magic items, including weapons/armor of bonus Z", so are hesitant.
When you broach the subject of magic items with them, reactions can range from anger, dismissal, or even "eyes widen in surprise" lol.
Adventurer's League used to be very conservative about magic items, to the point that I didn't start collecting any until we went on adventurers that allow for random loot, like Storm King's Thunder.