One possible pressing reason for the change is that, so far as anyone outside the company can tell, after seven years, Canonical remains unprofitable. Any investors other than Shuttleworth may be understandably concerned for their investment, and this pressure is probably a growing influence on Canonical decision-making.
Moreover, even if there are no impatient investors, a company that is unable to show a profit after seven years risks being identified as a failure.
However, another reason may be Shuttleworth's own frustration over his interactions with the FOSS community. In Shuttleworth's first blog entry, he states that "successful open source projects are usually initiated by someone with a clear vision and also the knowledge to set about turning that vision into reality," and mentions his strong interest in interface design.
Could Shuttleworth's calls for uniform release cycles and a focus on usability be not just practical suggestions for improvement, but also a bid to become the dominant leader in FOSS?
That is not a question you can ask anybody without the interview turning immediately hostile, but its answer might help to explain the change in direction.
If this really was part of Shuttleworth's motivation (and I do him the courtesy of assuming that he might also have been idealistic), then the bid for dominance not only failed, but failed specifically in an area that was personally important to him. For most people, such failures would be more than enough to explain an increasing insularity -- if you can't dominate the greater world, why not carry out your plans at home, and prove that they work there?
We will probably never know all the reasons why Ubuntu/ Canonical changed from the embodiment of FOSS hopes to more of a business enterprise. Given the high expectations that Ubuntu initially raised, perhaps the disillusionment is inescapable -- and discourages me and everyone else from sufficiently acknowledging that, in day to day operations, the spirit of FOSS seems very much alive at Ubuntu / Canonical.
However, at the level of strategic planning, the fact that something has shifted is undeniable. For those of us who remember the initial expectations, FOSS can only seem poorer for the fact.
ALSO SEE: 20 New User Misconceptions about Linux