I suppose one has to consider the amount of traffic a company such as Google would get to any support point they provided. eBay, for the longest time, had very few and fairly well hidden contact points.
As far as a fax is concerned, I would be a bit surprised if they had a public fax line at all. Faxes nowadays only seem to be useful for sending records and information that cannot legally be sent electronically. (typically a HIPPA issue, medical records)
As for subpoenas, I'd think a business wouldn't WANT to keep a fax line for the sole purpose of being served. Get yourself a process server and have them show up at Corp HQ if you need to serve them. Why encourage frivolous litigation with an open fax line?
And then there's people that will ring any line they can dig up if they are insistent on getting an answer about something. That's when someone will fax eBay a question about a seller not listing the item correctly. People using the wrong channels causes headaches all around. If you have something as generic as a fax, you have to have it well-staffed with people that are capable of figuring out what to do with pretty much anything that rolls in, regardless of whether or not it ought to be going there. People will do stupid things like try to send some legal notice to a fax that's meant for internal use by their maintenance department, and then when the person that gets it is like "WHAT is this crap?" and throws it in the trash, they try to say "well, we SERVED you, here we have the fax transmission report, you GOT it, why did you ignore it?" ("because you faxed it to the JANITOR, you moron") It's easier to just not have it.