Dear Nigha,
Your query about CEO taking interview is just of academic nature and just consider CEO is the Chief Executive Officer of the Company and all the operations are under his supervision and it depends on him that how many powers/jobs he wish to delegate to other officials and in how many fields he feel he has the knowledge, experience & time to take care. Please understand he is the source of all the authorities and every department and employee of the company is ultimately responsible to him, Even in case Company is having different COO & CFO still they too comes under his command. During my 34 years of experience in India & abroad I have seen that the major responsibility of HR dept is before selection and after selection of the candidate. It's their job to shortlist the candidates fix up the interviews and once they are selected, complete the paperwork and joining responsibilities. Please don't take it other-way. Actually you see HR people may be expert in man management but they are not experts in the operations, finance, marketing, commercial or technical aspects of the Company's operations.
Even where HR is empowered to recruit junior and lower management people for all the fields they generally invite department heads to interview and judge the capabilities of the candidates. In case of middle management and at senior levels it's always some one at VP/GM or CEO who interview & select the candidate.Moreover you must understand only CEO knows what type of person he wish to recruits and brings to his company and it's always best for the Company if CEO takes personal interest in recruitment's as I feel in small and medium size Companies CEO's are mostly Owners/Directors or very committed employees of the Companies and their direct participation in the interviews give them an opportunity to develop personal relations with new employees and this can be a big motivating factor for the joining officials. This also encourage the openness among the people working under CEO.
Most important reason behind my opinion is. now a days in many companies employee turnover has increased to an alarming levels. Many of the times Company recruit one VP/GM and he brings his old team from the previous Company just on the basis of his personal relation with his old subordinates and the day that VP/GM decide to jump to another Company whole team is ready to go with him as they were recruited by that VP/GM and feel obligated to accompany him, but in case if the CEO had taken personal interest in their recruitment it's normal that they would feel more attached to him & Company and may not just leave like that.
So Dear friend there is no harm in CEO's taking interviews it only helps in improvement of productivity, continuity and reduction of work for HR people.