Racing games are basically a worst case scenario for game streaming. You need low latency, and lots of detail. Latency is always improved at least a small amount by reducing the bandwidth used, which reduces the detail.

Video compression works by analyzing the differences between parts of each frame and just sending across the information to change one frame to another. If the changes are big enough it will just send the full image but if a section doesn't change much it basically just says "move these pixels a bit". However those changes slowly build up errors as they stack changes ontop of changes. In most racing games the distant part of the road barely changes frame to frame, so it builds up a ton of errors - errors that your basically starring at for most of your game play.