> They needed the space for other things like the new generation Taptic engine on iPhone 7
I mean, they didn't technically need the space - there was space for one guy to cram one into the bottom without removing the taptic thingy (although it did get shifted slightly) [1]
[1] super long video and not practical for an individual to do it, but shows that there was space and it could've been included. https://www.youtube.com/watch?v=utfbE3_uAMA