nobody has made a modern pistol chambered for the 7.62x25
That's not quite true. Russia and China have all made all kinds of modern pistols in this caliber, and Vietnam made a less modern pistol, but none of them can be imported for various reasons. Nor can ammo made in those countries.
The real problem is the ammo. Much like most other Soviet calibers, it never caught on nor entered production here.
The ammo supply and price are major roadblocks. New production ammo tends to be as expensive as .45 ACP, if you can find it. The surplus supply is spotty, if you can find it. While surplus is generally affordable (if you can find it), the days of $.10/round Tokarev ammo are more than a decade behind us. This is a cartridge that you will have to order online.
All of the surplus is corrosive. That means that lazy or knowledgeable shooters will cause all kinds of grief for the manufacturer.
All of the ammo is foreign. It would be very frustrating if future political action restricted importation of ammo.
The cartridge is just too long. It's longer than a 10mm. The manufacturer would need to tool up for just about a whole new pistol rather than massaging it to fit into an existing gun. To fit it into existing frames and magazines, you have to accept severely reduced capacity (J&G's 1911 conversions), or handload catrtridges with the bullets set back to reduce length (and risk high pressure).
It's a great cartridge, but it's too impractical. .357 Sig with lighter bullets isn't that far off, but offers more if you want it, and in modern pistols. Police trades also tend to be pretty cheap. In revolvers, .327 mag is extremely close.