Потому что компания Microfoft представила Git Virtual File System.
GVFS (Git Virtual File System), which virtualizes the file system beneath your repo and makes it appear as though all the files in your repo are present, but in reality only downloads a file the first time it is opened. GVFS also actively manages how much of the repo Git has to consider in operations like checkout and status, since any file that has not been hydrated can be safely ignored. And because we do this all at the file system level, your IDEs and build tools don’t need to change at all!...With GVFS, this means that they now have a Git experience that is much more manageable: clone now takes a few minutes instead of 12+ hours, checkout takes 30 seconds instead of 2-3 hours, and status takes 4-5 seconds instead of 10 minutes.
Линукс тут при том, что на него это тоже, возможно, портируют.
The Git Virtual File-System currently only works for Windows 10, but with it being open-source under the MIT, it likely will only be a matter of time before we see it implemented as a FUSE driver for Linux.