I do.
Why ever not?
Oh, so it’s this old thing again? See below:
Well, I believe I only played Duels when ‘forced’ by some stupid event or something of the sort, and it was miserable, I was glad to get it over with, so I think it’s good that they got rid of this useless mode, which was also such a burden to support. 
How do you feel about that? The point is: this kind of personal opinion or preference is no better or worse than yours, so it’s hardly valid grounds for decision-making.
Whether a mode is cost-efficient to maintain and so on is a different question.
What is it, bots again probably?
With that said, PvP has never been the Mercs’ strongest suit, to put it mildly, and it has been especially bad since the mode went into ‘maintenance’ due to persistent bugs, if you ask me.
But anyway, most Mercs players have played it for PvE, I think.