That is a very close minded way to look at things. Closed Source does not always = Evil and Opensource does not always = Secure. Competition and choices should always be sought for. Without competition, stagnation is as prevalent in open-source community as in closed source. I rather have the right to choose between a Mac, Windows or a Linux variant than someone making the choice for me.
So the problem is perpetuated - windows is the only platform that is basically guarenteed to have a market. So as a user of software, you'd stick to windows, and as a maker of software, you'd stick to making software for windows. Other platform is almost an afterthought. Unless web based software radically changes (i need to unzip a file - what web based software will do that for me?), this will not change.
There are probably other services/tools, because technically, there's nothing stopping you from unzipping files in the cloud, or in web based software. It's just the matter of uploading something and then downloading the content after it's been unzipped on the remote server. So it's just more expensive in terms of network traffic.
The availability of the tools that do that, other than Google Docs, is another thing. Honestly wouldn't know, don't recall ever needing it before.