After independence India was ruled by single party government for more than 50 years..
The Central government was controlled by North lobby & many states were neglected.. South & west states get some importance only when regional parties became a force at centre.
It is better for a diverse country like us to have a government which got representation from all regions.. We don't need a family rule or Communal rule.
See the results of single party rule for last 50 years..... 65% still under poverty.. 40% illiterate.. 45% unemployment. Caste hatred.. Communal violance... Terrorist activites.. Economic unstability.. degraded health sector,pollusion...etc..etc
List will be endless..
So it is better to have a front consist of regional parties..