Why is Dell still pushing products out based on Android 1.5??

I find it extremely weird that Dell will release Dell Aero smartphone based on the Android v1.5. Mind you that they released Aero recently in Aug 2010, when Android v2.2 is already out.

It's widely known ( I even thought it's common knowledge) that the reason for releasing products with the latest software/firmware because it usually contains:

1. Bug fixes
2. New features
3. Security fixes

By releasing an old version of Android, aren't they endangering the users of the smartphone? What happens if someone exploited a security vulnerability based on the older version? Furthermore, based on what I heard as of now, upgrading Android OS is not that straightforward and loss of data seems to be quite normal, unlike the iPhone.

So what's the reason for releasing Aero on Android v1.5? Bloatware issue? I'm afraid only Dell can answer this question.