Subtitles are actually extremely helpful in Hitman (2016), even if you can hear just fine. There is a lot of ambient dialogue in the game, but only the particularly useful/relevant stuff is subtitled. Or to look at it another way, you can safely ignore all the stuff that isn’t subtitled.
For example (and it’s been a while, so maybe some details are off on this), there’s an NPC in Hokkaido who has a conversation with one character about drinking and a conversation with another character about smoking. The conversation about drinking isn’t subtitled, it’s just fun background info about the character. The smoking conversation IS subtitled, because it’s there as a clue that you can find a pack of cigarettes (which can be used to take out one of the targets) in the guy’s room.