Most People decorate their homes according to what they like, the only rule in interior design is the colour choice there are rules so it is best to use the colour wheel.
When I am with a client the first thing that I need to know is the client single or living with a partner as both parties need to agree to the choices that are being made.
If the client has a partner and he/she is not present then in most circumstances it is not a problem, client then advises me on the likes/ dislike .
In interior design you can mix modern with traditional furniture.
VISION FOR INTERIOR DESIGN
Some people do not have a vision when it comes to decorating or making a room look nice, so they need help from the professionals in creating a room design.
Firstly there is a budget to be considered, and secondly the time factor.
The client may not want to change their furniture they may just want to change colour schemes, window treatments, reupholster furniture or add some loose covers with new cushions or move furniture around to create a different kind of space.
Some people are not open minded to dramatic changes depends on the age of the client. In my experience `I have had clients that say they want a dramatic change in the style and decoration after showing the client the interior design style that they have chosen which is computer generated they sometimes change a few things around as they realise the style they thought they wanted is not for them.
So in terms of interior design there are a lot of factors to considered before the final choice is made.