A corporate tournament has a hard stop that club sport does not: people are being paid to be there, and the afternoon ends. You are usually working with four to six hours, eight to twelve departmental teams, and a venue booked by the hour. The format has to be chosen to fit that window, not the other way round.
For eight departments on two pitches at twenty minutes a match, a full round robin needs about four and three quarter hours of pitch time — technically a full day, realistically an overrun. Two groups of four into semi-finals brings it to sixteen matches and under three hours, and still guarantees every department three games, which is the number that decides whether people feel included or feel like they wasted an afternoon.
Straight knockout finishes in four slots — about an hour and twenty minutes, since the seven matches fall into rounds of four, two and one rather than dividing evenly across the pitches. It is also the format where the finance team plays once, loses, and spends the rest of the day at the buffet wondering why they came.