In perfectly competitive product markets the firm must be fully efficient to survive. In the long run, firms only earn normal profit (see Chapter 5). In these circumstances firms must pursue profit maximisation as any other policy results in the firm earning less than normal profit and being forced to leave the industry (note that long-run equilibrium in monopolistic competition is also characterised by firms only earning normal profit)
For a firm to pursue a non-profit-maximising goal it must therefore be in either an oligopoly or a monopoly and be capable of earning abnormal profit. In such circumstances the firm has the discretion to be less than fully efficient and still survive in the market (see the concepts of x-inefficiency in Section 5.11 and organisational slack below)