Armies don't turn on a dime, logistically, and the Soviet Army has always hung on to equipment for long periods. Rifles, trucks, you name it. With the numbers of soldiers they had to equip, they probably issued everything in stock, no matter the age. The Russians also didn't care who scoffed at them. Some gun is better than no gun.
Even the US Army issues older equipment concurrent with the new stuff. Some WWII US soldiers and Marines carried 1903 Springfields.
The Army adopted the M9 in 1985 IIRC, but during Desert Storm I was issued a 1911A1 - in a Regular Army FORSCOM unit, at that. The unit didn't trade them out for M9's until 1992.
No joke. Our Stryker had brand new M2's from WWII. When I saw that date it blew my mind, 1944 if I recall right. They came in big wooden boxes filled with foam and were literally covered in cosmoline. Like dipped in it, bore completely stuffed.
At the SF armsroom, they actually had a few 1911's from WWII. I don't know if they actually still used 'em, but one guy had the SF gunsmith work on his own 1911 that he used. This was in '03. Wouldn't surprise me one bit if they still used 'em, I'm not a big 1911 fan so I never really brought it up.
In our armsroom, all M9's (for pistols anyway). The pistol was not highly regarded at all, most people that had to carry it looked at it like a paperweight. The M4 literally makes it useless today IMO. Our 1SG didn't carry one, made the arms room order him a rifle instead. Said he wanted a "real weapon". Who can blame him.
I hated those pistols, M9's, mostly because I had to teach them how to use them, they'd send the officers to the SDM school to qualify when they couldn't do it on their own. We'd get to babysit them and listen to how they shoot bottlecaps at 25m with a Glock but can't hit a silhouette at 10m with an M9. After a good cry, we'd show them how to hit the target. You'd be surprised at how poor of a shot most soldiers are, ESPECIALLY the officers, and this was an infantry division! They don't even really stress marksmanship anymore, just rates of fire. You have shoot 'til it goes click, shoot a lot, shoot a little, and cease fire.
As for who carries it, everyone on here pretty much nailed it and it is the same way today basically. Too engaged to use a rifle? Here, take this.