There is a multiplicity of reasons why we may require a larger home. Our homes have become multifunctional, no longer just a roof over our heads and somewhere to sleep. They are the hub of family life, and the centre of our recreational activities; we relax at home; we entertain there; many of us work at or from home; we pursue our interests and our hobbies from home, and we use it to display or store an ever increasing number goods and possessions. All of these require space. Homepage for anyone interested in investing their money for a new home. 
A number of people frequently occupy the same home and more may be added unexpectedly; we produce an additional child; adult children continue to live with us while they save to buy a new home builder Melbourne of their own; or one or more of our parents move in with us when they get older. There may be a multi generational family living under the one roof, all with different interests and needs; and this can lead to conflict if things become too crowded. Kids want their own rooms; parents need a place to retreat to on occasion; grandparents like some privacy: everyone benefits from having their own personal space.
We also do a lot of multitasking nowadays. It can be an efficient use of time, but often results in individual tasks taking longer to complete. Having to pack up and put away something before it is finished will delay it further. Even if we are multi focused, we tend to lose focus when something is out of sight. Special rooms or areas where our unfinished tasks or hobbies can be left temporarily can be invaluable. Many of us are also becoming multi skilled, pursuing various hobbies and interests, each of which may require additional, even separate spaces.
There are however multiple options for resolving these issues. The one most people consider first is extending the existing home. Home extensions commonly involve building onto the back of the house, usually to create a large multipurpose living area. However if land is limited the solution may be to build up rather than out, and create a multilevel house with additional rooms upstairs. If extensions are impractical for one reason or other, one option is to sell the house and buy a larger one. This depends upon us being able to find a house that meets our criteria. If we can’t, then building a new home may be the answer. This might involve buying a vacant block to build on, or demolishing the existing house and rebuilding on the same land. The advantage for new home builders is the opportunity it affords to have a home designed to meet their specific needs, including perhaps multi dwelling housing that provides a separate unit for grandparents or an adult child.
Ideally it will be a multilateral decision involving all members of the family, made after careful consideration of the relative advantages and disadvantages of each option. Ultimately though, unless we are multimillionaires, cost is likely to be a deciding factor.