There are various reasons why it makes more sense to buy a practice as opposed to trying to grow organically.
Specifically:
Actual client history, revenues, and results rather then projections and hope.
Established and trained clients and referral sources.
Trained staff.
Assistance and training by seller.
Opportunity for an additional revenue stream should you offer services the previous owner didn’t.
Existing office space and equipment so you are ready to work and bill on day 1.
If you already own a firm, significant bottom-line contribution due to the economies of scale.