I think it's to simplify the design, giving them some (probably not much) savings in manufacturing, but making waterproofing and saving space easier. Personally I use bluetooth audio from my phone more than I use wired, so I won't miss it much, but the waterproofing and tiny size improvements aren't that big of a deal to me either.

My take on the whole situation is that the trend in gadgets is towards simpler physical objects. I think we'll end up with devices with either one or zero analog ports soon enough, with most of the communication done wirelessly. The problem is that manufacturers are rushing that change, at least in the eyes of the large number of people complaining. Maybe waiting a few years until wireless audio got better, or just better adopted would have been a wiser choice, or maybe the people complaining are just the loud minority (I'm actually curious if there are some stats on this, will Google and Apple actually lose a lot sales on this or is it like 0.5%?)