Is a tire patch kit really necessary for urban commute? I'm cycling for urban commute, on well-maintained roads and bike paths, Vittoria Randonneur "puncture resistant" tires, and at no point on my ride am I more than 1/2 mile (usually within 1/4, I bet) from a bike shop.  I also presume that I'll never be without a wallet and cell phone and am in a city with good public transport.

Given that, is there really a reason to bother carrying a patch kit or extra tube with me?
Well, to answer this, there are a couple things to consider.  

1)  What are the hours or operation of the bike shops?  Do you plan to ride when the shops aren't open.

2)  Are you sure that all the bike shops will always have your tube size in stock.  Seriously, you think they would always have 700x32 in stock, but I've had it happen enough times that it's annoying.  Not to mention the number of times I've settle for using presta when I'm really supposed to be using schraders.

3)  How far do you really want to walk, and what is the penalty for being late?  Walking 800 m (1/2 mile) could take around 10 minutes. In that time you could have already changed the tire. Do you lose pay when you get to work late? If this happens too much will you be seen as unreliable, and get your shifts cut? 

4)  How much does a patch kit or extra tube and a frame pump really slow you down?  A patch kit can easily be stored in those bags that go under your saddle, or in your jersey pocket.  A pump can be mounted on the frame, and you probably won't even realize it's there.  

Personally, I don't think there's much reason not to carry a pump and spare tube.  Although it does seem useless at this point. I ran over a broken beer bottle on the weekend and heard and felt the glass crush underneath my tires. Thanks to gatorskins and tuffy tape, I didn't even have a flat.  I seriously question why I should bother.  But then 3 months ago I had a valve fail.  It's almost never the case that I get a flat from an actual puncture, but usually from pinch flats or other unexpected things.  I don't think I've ever had to use my allen keys on my commute, but I still carry them. That being said, the day you have to walk a mile because you didn't want to carry something as small as a tube and pump is the day you're going to rethink why you don't carry one.