Most new computers with a new keyboard and mouse. Most people don't need a second one. (And the HN crowd probably has a lot of users with KVM switches.)
This is why I've never needed to buy one of those $1 mice (some of which are very high-end). I have my own box full of them.
Although I shouldn't say "never". I have a box full of keyboards, too, but needed a real PS/2 keyboard recently and discovered that I didn't save any from the last time I did an equipment purge. So I had to buy one from the reseller (which was where I donated my old ones to begin with. It's not impossible that I bought a keyboard I gave to them!)