"The question of why so many Google products are classified "beta" – and classified thusly for so long – has knocked around the tech press for some time. However, no one really seemed to know the answer, at least no one outside of Google."

http://www.pcworld.com/article/151659/google_redefines_beta.html

This is an easy enterprise-business answer to be honest.

If you claim beta, you can put in your ToS that you can't always forsee and be liable for data loss, due to buggy code – hey it's in beta, right..

Also, once you go 'stable' you have to provide proper customer support, instead of staying generic.

And of course, if they loose your email account, 100% .. they never guaranteed you will keep it forever. No 'final' or 'stable' agreement you signed where it stipulated they guarantee to uphold the services, including ensuring you keep your account.

<< If you claim beta, you can put in your ToS that you can't always forsee and be liable for data loss, due to buggy code. >>

That's completely untrue. You won't find any free application that includes a terms of service which says that the company is responsible for data loss. Here's a quote from Windows Vista's terms:

"LIMITATION ON AND EXCLUSION OF DAMAGES. You can recover from Microsoft and its suppliers only direct damages up to the amount you paid for the software. You cannot recover any other damages, including consequential, lost profits, special, indirect or incidental damages."

For most Google services, you didn't pay anything, whether they're in beta or not. The "beta" moniker simply allows Google to say that this is not the final product and it might be changed significantly at some point.