1st Gen G17s were only made for a few years - and those years had VERY low production numbers compared to today. If I did my math correctly, there were only about 115,000 Glocks (G17, G18 and G19) made to the end of Gen 1 production worldwide.
Attrition - how many guns (not just Glocks) are lost to fire, flood, etc?
Finally, most guys that have older Glocks just keep them. I work in a shop and can tell you that for roughly every 10 used Glocks we get, 9 will have been made in the past 2 years.
USMCR 1997 - 2004
PAARNG 2011 - Present
Founder - Glock Collectors Club PA Glocker #39
Looking for G22 PE389US
Multiple Armorer Certifications