All of SharePoint's success must have gone to its head. It refuses to use SQL's Model database when it creates new databases. To recap, when databases are created in SQL, they are created using the same settings as System database called Model. Microsoft does a better job than I do explaining it here on MSDN.
When I do my SQL and SharePoint sessions I preach the importance of changing the default database growth settings. Unless you change them your Content Databases will be in Full Recovery Mode. For those that aren't familiar with SQL, this can result in drives filled with Transaction Logs. The databases will also grow at a paltry 1 MB at a time which is laughable for SharePoint. The Transaction Logs grow at 10% at a time, which isn't much better. While Full Recovery Mode is good for production environments, the autogrow settings don't make any sense. I tell folks to change the autogrow settings to something more reasonable like 1 GB at a time, and to pregrow databases so it doesn't have to happen during heavy use. This keeps database file fragmentation low, and users hopefully won't see any slowdowns due to database growth.
I was building a test environment today and I decided to automate some of this. I wrote a script that set my Model database to Simple Recovery Mode and set both data and log autogrow to 100 MB. Neither of those are good production environment settings, but for my test environments they made sense. Imagine my surprise when the next Content database I created had the 1 MB and 10% autogrow settings! It was in Simple Recovery mode, so it wasn't a complete loss. I couldn't believe my eyes. I verified my Model database settings were at 100 MB growth, they were. SharePoint was just dancing to the beat of its own drummer. I reproduced this in a few different farms and had some SharePoint admin buddies of mine verify it.
The moral of this story is that you should pay attention to your database settings and you'll need to manage them manually. You cannot rely on your Model database settings. This is especially important if you have a DBA managing your databases for you. They may expect SharePoint to copy the Model database settings.