It's not only that it's more fun, it's also usually the better path for self-promotion. Inside a company promotions often go towards those who have most visibly contributed to new projects. In open source projects that is of course not as prevalent, but even then many people will put open source contributions on their resume and "made big feature XYZ" is typically more impressive to recruiters than "fixed lots of small documentation and localisation problems".

I don't think this is justified, as (since the article correctly describes) over time maintenance becomes much more important than the initial feature creation. But at the moment this is the world we live in and people adjust their behavior accordingly.