I don't defend manufacturers that do this or anything, but personally I hate cords and want to go wireless for everything. Of course a headphone jack doesn't prevent me from doing that, but given the choice of two identical phones except for a 3.5mm jack, I'm choosing the one without.
Why have a hole that I'm never going to use that can trap dust, allow water in, take up a tiny bit of space and make the phone look less appealing (to me)?