The US does too.
I have posted quite a bit on mu opinion on the US using mercs. It is stupid and ultimately will lead to bad outcomes.
But it was the new hot crazy, and cheaper than having a professional army. No VA benefits
The difference is that while other countries may use contractors (mercs), those contractors are not a major battle force (they are used primarily for clandestine operations and security). With Russia, however, the Wagner Group is an essential battle element that is a recognized and integral part of the Russian military apparatus, and enjoys substantial authority in military operations.