There's a reason that they are the most used service pistol in the world today.
I've heard that claim for at least two decades now, and at one time I believe it may have been accurate. But I've never seen any real production numbers on the CZ 75 that would allow someone to verify.
The FN P35 Hi Power was probably the most widely used handgun in military service around the world.
But by now the Beretta 92 series, Glock, and Sig 220 series are probably close to or exceed the numbers of CZ's in service around the world in military and LE service. I honestly don't know which pistol has been made in the greatest numbers, but needless to say, CZ is very well represented around the world, and that's because it's an outstanding pistol.
I've been studying this issue for over a decade now. I believe the "most widely issued" claim was based on the sheer number of nations issuing CZs, not the actual number of pistols. An emerging nation with a Marxist-Leninist regime that gets a sweet deal from the CSSR for a thousand CZ-75s is still a country issuing CZs.
I highly doubt that the Hi-Power ever cracked the top 5 for "handgun in military service" by either number of issuing nations or total numbers. The 1911/1911A1 was manufactured in colossal numbers, and many nations in the Western hemisphere purchased U.S. surplus after WWII. The USSR issued the 1911A1, for that matter (Lend Lease). The S&W Military and Police, Tokarev, Webbley. and several Walther models would also be higher, especially if we count clones/copies/variants. Remember, revolvers are also handguns.
You sort of changed the basis of your argument. Are we talking military use or law enforcement use? I'm pretty sure S&W K-frames are the leader if we include law enforcement.