Importance of kickoff meeting

The main goal of the kickoff meeting is to let all team members, customers, and stakeholders know that the project has begun and make sure everyone has a common understanding of the project and their roles. It doesn't matter whether it's a small, medium or large project.

Apart from what Anish has said, a kickoff meeting also set expectations and establish guidelines to help complete the project on time and within budget. The only difference I could see is the magnitude of ceremony as a bigger /complex project means more number of stakeholders (top management, client, team members meaning all parties involved in the execution of the project)

Excellent points already from Anish and Najam.

Some additional aspects that I cover in my kickoff meetings (for projects of all sizes):
- Explicit reinforcement of project objectives, success criteria, and KPIs
- Conceptual traceability matrix between objectives, KPIs, and project activities
- Team introduction and building activities (ice breakers, games, etc.) to give the participants an association of fun and adventure before stepping into the project.

You are getting everyone on the same page and formally getting their COMMITMENT

Consider your kickoff meeting as a type of preventative activity to save the much higher costs of firefighting further down the line. It provides the earliest opportunity for a PM to defuse any myths or misconceptions regarding the project.

Of course, like all PM practices, it should be tailored and scaled to the needs of a given project.

Kiron

It is often the first time many team members meet.

You are getting everyone on the same page and formally getting their COMMITMENT

Agree with Anish. You should conduct a kickoff meeting to let the team and stakeholders know each other, under objectives of project, ballpark estimates, timelines, milestones and may be budget of project.
If the project is huge, PM can conduct multiple kickoff meetings for multiple phases or milestones.

The kick off meeting is essential to set the stage and share information with the project team, to ensure that everyone is set up for successful execution

None except to socialize and inform the project is there. You have to do your work "to sell" the project.