Yes they're still being sold because we're still getting those in some Dell machines here. You can still buy 17-19" 4:3 monitors too even though wide screens are cheaper!
Having worked with .gov agencies, the amount of bull shit that they need to go through to purchase ANYTHING some days is mind numbing. We had to:
Buy from specific vendors who had a contract (so no amazon/newegg options)
Only buy specific products (ex: GSA merchandise)
Fill everything out in triplicate by hand and wait for signed approval (taking weeks)
Specify the cost center for purchase and pray that there's money in the budget or wait for someone to determine whether something like a HD truly is office vs maintenance vs misc equipment
Why all of these hoops? Ultimately to have "transparency" in our purchases so when an external entity comes in and looks at the accounting books our collective asses are covered because we purchased from a contract retailer instead of bobs-hard-drives.com.
For what it's worth, the purchase order for that XP machine with the 80gb drive was probably initially submitted when that was a "normal" size