Because it's an open project that symbolizes the freedom of the Internet, besides from being a wonderful browser driven by passionate people from the company and the community.
Also, it's a matter of respect. The fight for an open web and liberation from microsoft tirany has made possible to have this huge network of knowledge that is changing the society from its basis, allowing truly free exchange of information and culture and an universal way of communicating with whoever you want.
I know chrome is better in many aspects, but represents the desires of a company that only wants to be richer. The open web google promotes it's just part of their expansion plan, and I need to remind me this each time I use their wonderful browser.
Sorry for extending but this topic always touches feelings
