MJ has given you one very good reason, and having 'been there and done that' I can assure you that taking 10 aircraft across the busy UK airspace at high level can result in significant extra miles flown and a lot of work for a busy ATC system to get 2 separate formations around, and if there is any weather about, getting 10 down (no, not a crossword
) can be a bit of a challenge. Straight lines can be drawn without worrying about airways, and only minor deviations are required to avoid CTAs and the like. Throw in to that that if the team regularly 'arrived' at their display site in groups of 3, 5 minutes apart off an ILS, what would the audience think of it so far................
If the distances are significant, it is done at high level with the associated penalties.
Edited for Onan: I think, with the new Bush/Blair accord, it is done with AWACS? Of course, you show your age talking about a 'VCR'