Social engineering, within the context of cyber security relates to the human factor within a business, whilst it may be possible to have the best possible perimeter security solutions, the human element can effectively render them useless should an employee unwittingly provide access to the internal network.
Regular social engineering assessments will especially benefit larger organisations who regularly interface with customers and have a large turnover of staff.
Businesses who have externally and/or internally facing servers will benefit from regular network penetration testing.