Marketing
Marketing has hardly been Opera's strong point over the years.
Why is it that so many significant upgrades and changes appear in x.5 versions rather than new major versions?
Any fule kno the press only really take an interest in major releases with all the x.01 releases being completely ignored and the x.1 releases being lucky if they get a 2x2" box on page 37.
By the time the next major release comes out (which could be a couple of years later), the new features are either old news after being given a fanfare in rival browsers, or the lazy reviewers only just notice them and list them as being new to version x.00, adding that Opera 'finally' catches up with its rivals.
Opera 9.5 was the same, with a hugely rewritten rendering engine, javascript interpretor, mail client, skin and other notable changes.