The only reason for promoting you to partner

The only reason that you are offered partnership within a firm is to increase profit per equity partner.

That's the only reason.  

Existing partners will therefore ask questions such as:

• How long will it take for your client base to grow to meet PEP expectations? (this year?  three years hence?)
• Do you have the personal qualities that will make this more likely (team player, plays well with others etc)
• How will your current client base can grow, develop and link with others' to bring in the money 
• If you're not offered partnership:
  - Would you leave?
  - How much work would go with you?
  - How much work that we currently do would be affected, and for how long? 

                                             ...And would profits go down?  

This doesn't mean that the firm is just focused on PEP.  The law firm is a business, however, whose duty to the shareholders (the equity partners) is to maximise profits.  

The best way to do this is to create satified clients (Peter Ducker's Definition of the aim a Business). Profit is the way we keep the score.