For perspective, the headband of intellect is an "uncommon" magic item in the Dungeon Masters Handbook, which means that it is considered appropriate loot for lvl 1-4. A committed wizard will want a 20, so the headband isn't particularly useful beyond the early levels. I use it purely to boost INT skills in BG3, which is a fairly niche application. It can make eldritch knight or arcane trickster slightly more effective.
One big Caveat... in 5e the headband requires atunement to use, and you only get three of those. So once you get to higher levels almost everybody is going to want something better. The headband is a bit better in BG3, since the only opportunity cost is that you cannot put something else in the head slot.
In PnP you would never build a character concept and min-max 8 Int around a particular item because there are no guarantees you will find such an item. Or be able to keep it if you do.
In a video game you can just go get it, and it's unlikely you can ever lose it. It changes the game completely and suddenly the "8 Int build" is great because you get to put so many ability points elsewhere. Stupid, but powerful.
