Well like I said, players already have the option to play sturdier races like humans, dwarfs, and qunari, so imo it's only fair that elves be slight so that players can have that body type option.
Regarding body types though, I will say I hate how they've slimmed down the female dwarfs. Lame, BioWare 
I definitely agree that I like that elves are slimmer because as a person with a slight body type I like the representation. Though I wish I also had the option to play as a slim human, because the implication that slight humans are out of the ordinary is a bit unnerving, and my human Inquisitor is so very tall. I feel like it's often taller humans irl who are considered attractive and my small size has always bothered me in that regard, so I would have felt better playing as a small human instead of having to identify as a non-human, haha. I have nothing against elves, of course, I just like playing self-inserts and I don't identify much with elven culture even though I can respect it.
Also, in Inquisition, everyone's boobs are so big. Even the elves. My tatas are not quite so large. LOL. screaming.
I understand that it would have been hard to implement body size sliders in Dragon Age since they might end up with size overlaps between the different races, though. Oh well. It's not a big deal and it didn't bother me that much, but I just felt like I had to say it.