Well, from what I know its just cheap, comfortable and multi-purpose. Since its roomy enough to fit a sweater or two underneath you can wear it during winter, keep it unzipped during summer and there's at least 5 or 6 pockets in every suit.
You can wear one for housework, outdoor activities and just to get lost in the crowd. I prefer trenchcoats though, thicker material.

I think you mean track suits. And it's probably a status symbol to wear Adidas. After the USSR broke up, they finally had good access to western clothing. Its the same with cars, pretty much all the people with power and money drive foreign luxury cars, especially German ones. There are some exceptions, like Putin prefers his custom ZIL and other stuff like Lada Nivas and an old Volga, but he's a staunch Soviet/Russian patriot so it's really not surprising.