Lyxen
Great Old One
I theory. But frankly, the DM just deciding that the PC cannot use their social skills they invested character creation resources in is not great. The GM gets to decide what happens, but it would not be cool if when you declare that you want to attack an enemy, the GM just declared that the enemy dodges without letting you to roll. The general assumption is the the players can use their PCs skills to get the things they want.
The game is extremely consistent here, and it works well, once more the players only describe what they do and the DM allows the technical use of the skill when he deems it appropriate: "Pay attention to your skill proficiencies when thinking of how you want to interact with an NPC, and stack the deck in your favor by using an approach that relies on your best bonuses and skills."
This does not mean that the DM will allow you a check (he might use a passive, he might decide on automatic success or failure, etc.), but as you say, a good DM will make sure that you have fun by not frustrating you about ignoring yout skills.
That being said, a DM can also decide to totally ignore them when the circumstances warrant it, for reasons that only he knows, and a player should have the good grace to recognise it. It's all about balance as well.