I'm confused by the confusion.
Let's say that live and work in NYC. During a trip to LA, I decide to schedule a conference call meeting for Monday, December 2 for 2pm EST. Some of the participants will be in NY and some in LA. Since I'd be in LA at the time that I'm setting up the meeting, I'd key it in as 11am since that's when it will be for people in the time zone that I'm working from as I enter the appointment. The east coast folks will see it as a 2pm meeting. If we later add someone in Chicago, they'll see 1pm.
If the confusion is about why the current time zone is a factor at all, the answer is that the time zone is a factor so that offsets can be properly computed for other users. Just listing a time (i.e., 2pm) isn't enough to specify when a meeting is unless one also knows the time zone (and applicability of daylight saving time). This is exactly how it is on your computer, except that your computer doesn't typically know its position so it doesn't typically adjust its time zone for local time, as your phone does.
If the confusion is about why Microsoft didn't provide Windows Phone with the ability to let users specify a time zone along with an appointment, we'll just have to assume that they left it out to reduce complexity. I wish that they'd add it in because it would make cross-timeone and out-of-home appointments easier to enter. As it is, I usually key in cross-time zone meetings from Outlook directly to avoid the confusion.
I recently traveled from PHL-LAX-AKL-BNE and back; I did it across the end of DST in the States. My appointments where scattered across the International Date Line and multiple DST settings: I left the U.S. during DST, entered New Zealand during their DST, went to Queensland (where, like Arizona, they don't observe DST even though the rest of Australia does), and returned home to standard time. All of my flight times and meetings were correct because they where keyed in to desktop Outlook with time zone offsets. If I had ignored those offsets, I'd have missed planes and even been at the airport on the wrong days.
How to Turn Off Outlook Calendar s Overzealous TimeZone Feature on