Something I encountered several times now is that when there is a discussion about a rule because there are multiple ways to interpret it or that it offers no help at all for the DM to adjudicate it someone comes and praises the rule as being intentionally vague so that the DM can interpret it.
My question is why? Why is it a good thing if a rule is vague or even not usable without houseruling or when the books give the DM no guideline, suggestion or other help in resolving something?
The idea probably is that this somehow empowers the DM, but why does a DM need vague rules to be empowered? He can already change anything he wants. And if the intention is to have the DM rule by himself, why make it a vague rule instead of a suggestion with helpful guidelines on what to look out for and how this ruling fits into the game world?
That would be a lot more helpful than to make a vague rule or a table with entries so vague that they do not help at all (the latest example being Carousing and not having any suggestion about what getting arrested actually means of being able to build strongholds and trade posts with no explanation what they represent and how they can be used in game).
I can only speak for myself. I am both a player and a DM.
Precise rules are supposed to make the game easier by taking the need of adjucations away. There are no adjudications needed in a game of chess, therefore there are no rules discussions, no need for a referee and no protests.
A RPG is a kind of game that traditionally goes so far in depth and variety, that has more rules than any other game. There are both rules-heavy and rules-light RPG however. The idea is always that what the rules don't cover, the DM has to make up something. Then it's up to each group to decide if they want more rules and supposedly less make-ups, or viceversa.
The problem is that more rules always invariably leads to more problems, because nobody can ever manage a massive rules design without making some mistakes, or failing to predict how different rules interact. More rules require either more designers (adding more chance of errors because of mis-communications) or more time (adding more chance of forgetting what was designed a long time ago). Just think about what happens to RL countries which have very intricate laws instead of a smaller and clearer set...
So in my experience rules-heavy systems don't really decrease the need for making up something... they could do so in theory, but in practice they only cause more discussions, more enmity between players and DMs (when someone starts believing that only he is getting the rules "right" and sees and treats the others as morons). Typically, it still ends with the DM having to make-up something, but now with one or more players who have lost trust in the DM or are bitter over losing their little rules-lawyering battle.
My interpretation is that the WotC designers at this edition round identified SOME critical areas where traditionally debates are very frequent and can cause the whole game to halt, and "blurred" those areas with the purpose of changing the basic assumption that there is a "right" rule. When there isn't a right rule, you cannot avoid rulings, but you don't have much ground anymore to dissent on such ruling. Thus if there is no "right" way to handle hiding/concealment, the rules lawyers in the group shouldn't even bother to start debating, because the DM's adjudications are not based on trying to understand what is "right" but only on what "may do the job well enough for our purposes".
[Note that rules-heavy vs rules-light is not exactly the same as rules-strict vs rules-vague. Chess is fairly rules-light and rules-strict. D&D is traditionally rules-heavy and rules-strict, but 5e modularity makes it so that you have a range between rules-heavy and rules-light, and you can choose that (e.g. you can use Basic combat rules, and play the rest of the game through RP only). It is also still fairly rules-strict by default, except a few specific areas, but the books also explicitly say you can loosen that strictness for the game's sake]
