The newest baseline Dell XPS 13 (not even Inspiron) comes with 4 GB of memory by default. The very idea of an extra 8 GB is hilarious because manufacturers haven't kept up with the times (my laptop purchased 9 years ago had 8 GB), and by extension the median consumer's laptop hasn't either. Nobody has an "extra" 8 GB outside of people with the money to just unthinkingly buy the top of the line model or developers who know what they're doing.
We're talking about buying extra memory, not defaults. And while an XPS 13 is trying to be a macbook, on an XPS 15 you just pop open the back cover and shove more memory into it.