Like so many other things, it's that which you don't appreciate until after you've lost it. I was a Metropass holder for more than three years, and in that time I had the run of Toronto - I could go where I wanted, choosing my own route out of the ones available, with only a simple magnetic-striped card in my wallet. I didn't have to think ahead, really - I didn't have to plan intricate A to B to C jumps to make the most out of tokens or transfers.
Now, of course, that's gone. The day after I landed in Toronto, I thought it might be nice to ride the subway around the downtown U, from St. Patrick to Dundas - but then realized that it wasn't to be, not with no money in my pockets and TTC collectors most definitely unwilling to accept a TransLink 2-zone December monthly pass. I couldn't just descend into the system anymore at a whim, to let it take me where it may.
Even in Vancouver, it's similar. My 2-zone pass restricts my movements during the prime hours of the week; though Surrey is just across the river, close enough to see from my window, my freedom to travel there by transit isn't complete - I have to stop and plan ahead, if I'm ever presented a reason to go to Surrey or Coquitlam or the communities of Delta.
It's not something I ever really considered before - it was just my inability to pass through the TTC's gates with a swipe of my Metropass that really brought the realization down. It's heavy, in its way - something so familiar, yet unreachable.