ActiveRecord#touch behaviour in Rails 3

In Rails 2.x, calling touch on an ActiveRecord model would update the
'lock_version' on the model, if it were present.

It would produce something like this in SQL:

UPDATE `foo` SET `updated_at` = '2010-07-23 10:44:19', `lock_version'
= 2 WHERE 'lock_version' = 1

This would ensure that your optimistic locking policy will be followed
should another concurrent update occur on that row in your database.
Rails 3 no longer updates the 'lock_version' column through the touch
method. I preferred the Rails 2 behaviour, I was wondering if anyone
knew the reasoning behind this change?