[y4mi]

Both sharelatex and overleaf support git. You can pull/push directly to their sites or pair them to a GitHub repo iirc.

It's significantly easier to do collaborative editing of latex files with such a web service. But even a single person might want to use them, because maintaining latex dependencies can be bothersome.

[carlosdp]

This, the dependencies are annoying to deal with. With ShareLatex, it "just works"

[Tijdreiziger]

A local MiKTeX installation handles this beautifully (MiKTeX is a LaTeX distribution which comes with a bare set of default packages, and then downloads packages from the internet transparently upon compilation if they're necessary).