The Crucible maps only have a certain number of spawn points, of those spawn points, the game will try and place you as far away from enemies as possible (out of available spawn points). For example, say there were 6 spawn points (not accurate) and 3 had enemies approximately 5 metres, 2 had enemies 12 metres away and 1 had the closest enemy 20 metres away, the game would spawn you on the last spawn point mentioned even f there were still enemies nearby as it is better than the other options. another issue may be that if multiple people are respawning at around the same time they will be allocated a spawn point and you may not (for whatever reason) be able to spawn at the same point as them (different team, free for all etc.).