My last 2 cars were at least 10 years old and still had both keys (granted they were 911s), my current car is 13 plate and has both and my wife's focus is 62 plate and has both. I don't think most are missing, I'm not sure how you'd even loose a car key mainly due to how much they can cost.
its quite easy to lose keys.
look on ebay , some people deliberatly keep the second or even third keys back when selling the vehicle to get extra from selling on ebay. used to be a scam around the auction houses that extra keys went missing and then turned up for sale on auction sites.again my daughters zaphira had 1 key due to a messy divorce she got the car he refused to hand the second key/handset over , took me quite a while for it to sink in that if she lost the key she was stuck with a dead vehicle and major expense eventually she took my advice and got another ordinary key cut and reprogrammed at the local tescos (yeah i know but they have a timsons outside the place lol cost her 30 pounds if i remember and the lost key (ahem) removed.
