I made Duncan conscript me on my Dalish Elf begging the clan not to abandon me and Duncan said he would drag me kicking and screaming to Ostagar if he had to. So why do I go willingly all of a sudden? Where is the dragging part? I am sure along the way to Ostagar there would have been a chance to try and escape from Duncan.
Would have been a fun alternate start if they showed Duncan dealing with a pissed off elf who he had to force to come instead of my elf just walking willingly into Ostagar.
A protagonist of every background has the option of saying they don't want to join, not just the Dalish elf. And in every single one of them, they wind up changing their minds and coming willingly. You can headcanon that your Dalish kicked, screamed, and tried to escape on the way to Ostagar (since it's kept blank) but then got with the program by the time you arrived. What we're shown on screen though is dozens of writers and animators with limited budgets who don't have time, resources, or desire to waste it showing the protagonist throwing a screaming hissy fit like a child resisting going to the dentist.
To paraphrase that dad from Monty Python: You're joining the Grey Wardens, so you'd better get used to the idea.