I think one of the great things that Drupal has done is raised the bar for the use of version control by PHP developers. It's one of the things that has set us a bit apart. CVS branches are another level of complexity...something we need to spread even more to improve the quality of our code and ingrain best practices.
HOWEVER....think of sandboxes as a "safe" place where you can experiment? Probably not something we can do indefinitely....
Maybe, either through the Drupal Association or through a friendly neighbourhood Drupal company, we can offer a CVS space for anyone...
There are some existing free CVS spaces, too -- here's one that I found:
https://freepository.com/services.htmlMaybe part of the handbook write up on sandbox (anyone have a link? ideally it should mirror in part what contributions/README.txt says) can gather some of these free resources. I opened a documentation issue for this: