There's a likely chance your inquisitor'll be recognized instantly as Dalish due to the markings on his/her face due to interactions with certain characters.
There can be other ways to identify you as Dalish. Most people will have heard of you by the time you meet them anyway.
I assume they want other characters to be more reactive to your race/background. Having vallaslin are the easiest way for other characters to know you're dalish from sight alone. It was probably just easier for them to require it than have to have a character without them explain that they're not a city elf every time it came up. Maybe it saved on the word budget.
I fear for the Human story then, considering if simply explaining the tattoo away was too costly to be practical, how much shallower did they have to make the humans who have two very different backstories.
This thread if filled with posts about how important it is for a dalish to have them. If you refuse to see them because you want your character to be the exact way you want or else it can't be "yours", then there is nothing else I can say to you. It seems you just don't want to be a Dalish elf. You want to be a regular elf and you want Bioware to facilitate that for you.
And you're right-- your character is what you decide it to be with the options provided. One of the options is a Dalish elf with Vallaslin. Enjoy.
I was just answering your part about "Well, your character..." in your previous post. And I'm fine being a Dalish Elf, if I can be a rebellious one. That is a compromise I can live with. But no, we're stuck with one who is a loyal servant.
Having a Dalish without the tatoo being sent to such an important mission would be like making Shepard 12 years old at the start of Mass Effect.
Options are nice. But if the devs decide they clash with the lore too much, so be it. Lord knows Dragon Age needs to stick to its lore every chance it gets.
Besides, who says that getting a tatoo = super duper loyal Dalish? You could easily chafe under your clan's restrictions and still get the tat because it's expected of you, and use the Inquisition as an opportunity to break free of that. Dialogue options are still a thing.
Nonsense. An adult is different than a preteen, both physically and mentally. The only biological difference between a Dalish with Vallaslin and one without is that one has blood and ink in their face.
Getting the tattoo is agreeing to devote your self to the clan, so I would say that counts as "super duper loyal". You could get less loyal afterwords sure, but even if you got that way the day after getting marked, that still means that for 90%-45% of your life you were devoted enough to them to give your life to them by the time Inquisition happens.
Not necessarily.
I can be conflicted.
I am loyal to my clan because they are my family, and the ways of the Dalish are all I have known. I may have wanted to run away from them for a long time, but severing all ties can be hard. Even if leaving would be the best thing for me, I may struggle with it, so I get my Vallaslin and act like a good Dalish. I silently suffer. Until an opportunity presents itself. 
Instead of loyalty, you should say love. You can't be loyal to something you want to run away from, and yet you can stay for love.