In the case of non-execs, they are often insisted on by investors. They are seasoned board members to keep the execs in order, that kind of thing. They have little operational interest in the company, and instead bring 'corporate governance'. They have a part to play in managing the board, not the company. They make investors feel better about investing in a company run by some technology upstart with no track record. In the UK they would probably be senior (perhaps semi-retired) auditors or corporate lawyers. They may also be people with a track record in that industry, designed to open doors.
Institutional investors tend to be pretty conservative, and these are their sort of people.
Institutional investors tend to be pretty conservative, and these are their sort of people.