For these cases, I was very careful to say "harder difficulties" and not "normal difficulty".
- Bioshock
Here's a few quotes from the developers sourced from
an interview where they talk about "survivor mode":
This was pretty much what I was saying. It's not the best example of an "intended experience", but it works as an example of mechanics that you only really NEED to use because of the harder difficulty.
To address what you wrote: Yes, you probably can just use guns on Normal. However, I remember ammo being more scarce (my most recent memories are playing the Remaster, which rebalanced the game), so I had to use my melee weapon a lot, especially in the beginning. If you relied only on bullets, you'd probably run out of ammo. That's what makes you use plasmids. In the case of Survivor, even more so.
- MGS3
On harder difficulties, players will spot the dead bodies, go on alert, call in backup, and then shoot you to death. On normal, you can probably get away with it and beat the game eventually, but you'll still probably die a lot. Depends on how much of the game you've memorized. Alerts are dangerous.
- Witcher 3
Let's assume our hypothetical players aren't exploiting an OP technique. In that case, they'd have be more reliant on potions, oils, bombs, etc as they advance in difficulty. During my playthrough, I only started leveling signs after I had made significant progress into the sword skill tree, so I didn't have your experience.