The need to build a custom home has many reasons and it would vary from one person to another. But, in simple words, the core reason why someone would want to go for a custom home is that they would want the home to be exactly how they want. It is not easy to find a production home to be exactly as you wanted. It is very rare to find one. Hence, the easier option is to design and build a custom home.
People who have home offices would have much bigger requirements from a custom home. In fact, after the pandemic, working from home has become the new norm and the need for custom designing home offices has increased.
Some people go for the option of buying an existing home and custom designing the home to suit their needs. It is also called home renovation. This can turn out to be a little less expensive than building a brand new custom home. But, the end result may not be as good as building a new custom luxury home designed completely afresh and built from the ground up.