There have been many defenses made of Spock's emotional displays in both STID and the 2009 film. Even if I agreed that these displays are fully justified given the plot, I wouldn't agree that this version of the character is nearly as interesting as the one we've come to know over the past 45+ years.
"Interesting" is so 1960s. The question for any part of the Hollywood remake industry is how to make the character profitable. Yes it was cool and all that the original Spock was all, like, weird and alien and stuff... but does today's teen really get that? Or want that? Played as more of a repressed nerd with anger issues and elf ears, he really gets at the emerging "emo" market. Plus you can sell it to the fandom as a call-out to all those times in old Trek where Spock lost his s**t. It's win-win.