The 14 inch tires that many people are using are what we refer to as European Commercial tires or Euro tires for short. They are more prominent in Europe and Asia where you see the smaller delivery vans, transporters and such. These tires are made by several manufacturers including Kumho, Hankook, Continental, Yokohama, etc.
The reason you see many using Kumho, is they are usually easier to find here in the States due to Tire Rack distributing them....... but there are several other brands available.
These Euro tires are sized just a hair different than what we are normally used to dealing with. I explained it more in detail a few years back below:
Tire Choices: I'm confused!
The reason people are turning to these Euro tires, is the fact you can't find a 14 inch ST tire with any ply rating higher than C (6 ply). The Euro tires are D (8 ply rated).
However, if you have 15 inch or 16 inch rims, you can find the ST tires in higher ply ratings, such as D (8 ply) and E (10 Ply)....... and are thus not as limited as you are in the 14 inch sizes.
Hope this helps.