What does "adult" design or decorating mean to you?

My husband and I bought this piece over the weekend (Kijiji - a steal at $250!).  It's a well made and practical piece as it stores a tonne - as you can see from the beginnings of my "propping" (yes, I sometimes "prop" my house).   However, the reason I'm writing about it is because of something my husband said: "I love it, but it makes me feel like such an adult".  And I totally know what he means, as I'm sure many of you do.  What's funny is that my neighbour said the same thing to me a couple of days ago about her kitchen.  She has just renovated it and put a different, funky knob on every cabinet because she didn't want it to be too adult.  

It's not that we aren't adults - we all have kids, own houses and vehicles, hold down steady jobs (I'm getting overwhelmed with adult here!).  It's just that some things FEEL adult.  I think adult-feeling design is when things feel intentional and cohesive - we aren't just using the hand-me-downs and hodge-podge street finds anymore (although this is still one of my favourite ways to acquire furniture).   Maybe it's that we are starting to tailor things to our style with a big picture in mind, instead of a more impulsive "this is a cool colour" and painting it?  I'm not really sure what makes something "adult".   Investing more in it?  It reminds us of our parents?  Of what we imagine adults decorating with?   It's hard to really pinpoint where the feeling comes from.   But, I hear it from enough people to know that it exists for many.  

It's not always a negative thing either.  I think my husband is okay with the piece feelig a bit "adult", as long as his house doesn't become too adult.   One thing I find interesting is how most of us seem to understand this feeling of "adult".   In my profession, sometimes all I have to say to someone is "Does it feel too adult?" to determine if they like something or not.   Or, to the contrary I say "Do you want it to feel more adult?" and this will help them decide.   Which goes to say, we all know what "too adult" or "not adult enough" is and feels like, it's just hard to define what makes it so.  

What makes something too adult for you?   Or, not adult enough? I'm curious and fascinated by this topic and would love your insights.