Comment 21 for bug 578045

@mpt is correct.

Having a well known PPA with a good reputation is better than being an official project member. You get most of the benefits of being a project member with none of the overhead costs of officially joining.

The community is familiar and comfortable with using Launchpad to get current software. PPAs provide the easy 80% of an app store implementation for Ubuntu.

The has the side-effect of making Ubuntu sticky. People that try to leave Ubuntu often discover that they depend on the convenience of PPA packages. This dynamic probably explains the Canonical Ltd position on the https://bugs.launchpad.net/launchpad/+bug/188564 ticket.