Goodbye mails from hell

Of course my working experience so far spans just two consultancies, but I gather the following works similarly in other consultancy firms: In my line of work apparently it's customary to send your colleagues a goodbye mail when you leave. Something to the tune of:

"Hi, I'm John Doe and after 5 years with the firm I've decided to leave to start my sheep farming business in Australia. Thank you all for all the hard work on projects Hard, Tough and Nasty. Farewell..."

Now, there's couple of things I don't understand in this matter:

1. We do have a global mailing list, and apparently it's for goodbye mails. So I may get greetings from people I've never met, will not meet (because they're leaving), and may or may not care about anyway. Why does everybody need to know you're leaving? I didn't need you before, I'm not going to ask for you now, am I?
(Don't get me wrong; I would like to be kept in the loop about people I worked with before. Just that this doesn't include everyone.)

2. Most people who leave find it noteworthy to state how many years they've been with the company. Why is that? Am I going to care more because you've been here for one year or for eight?

3. All these mails start to look like one another. It's greatly disturbing that people have absolutely no sense of creativity in this matter. Or does a template exist that people fill in when they hand-in their company car? Something like:

- fill in your tenure in years (half years allowed)
- list the companies you've been assigned to (maximum of 10)
- state reason for leaving (max. 200 words)
- leave a forwarding address
- enter a statement with some pleasantries for your ex-colleagues (no profanities please)

4. oh yes, the forwarding address. I don't know about the people who write them, but I would make sure the people who need to know my forwarding address, get it. Everyone else, not so much.
If anything, it is a bit cheeky to assume anyone you don't know would like to contact you after you've left the company. There's only a couple of reasons that this might be useful for: stalking or recruiting.

Oh well, when it's time to leave your position, let someone else write your departure mail. Nothing says more that you've arrived, than when your manager writes your departure mail for you.