There's a large range of normal social needs and that's fine. The problem is when a person becomes too dependent on another to fulfill those needs, be it their children, partner etc. Being too dependent on living through your children is a particular burden because it's a relationship that should change and evolve from a totally dependent baby to being an adult with autonomy in their life. Even when adults continue to live at home, within reasonable house rules they should have the freedom and independence to live their own life.
Being a parent's emotional crutch is very damaging to that child's relationships.
Having lost a parent in childhood and growing up with a parent adjusting to fairly early widowhood, and being supported by a network of friends, it was always important to me to spread my needs. As much as I love DH and the DCs, there is plenty of family time as well as chance to develop our own interests and networks. In the absence of local family support, those friendship networks are very valuable.
I'm currently a SAHM because I feel it's best for our family's needs, but maintaining my own interests is healthy for me and the DCs, that they understand that their DM is a person with needs beyond fulfilling theirs.
Our way is certainly not the only way, a more self-contained family approach is fine as long as it doesn't go into the realms of emotional dependency.
There's so many DM/ MiL threads where there is too much of this emotional burdening.