As far as the cash vs plastic argument goes (not going to bother quoting everyone who's mentioned it)
-Not all businesses accept debit/credit
-Most banks charge transaction fees for using debit (where I'm from anyway)
-Although it's easy to go online and see where my money is going on my bank's website, it's also quite easy to loose track of how much money I've spent while I'm out; taking out cash ensures that I don't absent-mindedly overspend. (it's like a self-imposed allowance)
-I just prefer exchanging tangible, physical money to electronic money.
-It's easier to use vending machines if I want to
-It's much easier to give tips with cash (I'm generous like that)
-It's impossible to lend a friend a few bucks for bus fare (or something) with plastic (again, I'm generous like that)
-I like the jingling noise coins make : D
And for the "get a wallet with a coin compartment" argument
-The wallets in stores I've been to have small coin compartments, I haven't seen one with a sufficiently sized coin compartment yet.
-I'm Canadian, I don't have $1 bills, but "loonies" and "toonies", so I have more coins than you American commenters
-Wallets tend to get pretty bulky when they contain coins, it's easier to have them in a separate pouch I find.
-The nice looking leather wallets (the ones I prefer because they look better and I find they're more durable than other wallets) tend to not have coin compartments.
-I can get a coin pouch for just over a dollar (yay for dollar stores), so it's better for me to just get one of those than it is for me to replace my entire wallet (a fairly good looking leather one)
btw, nice to see you back Katori