Toroidal Transformer Location in Chassis?

Can anyone explain to me why many diy amplifiers have the toroidal transformer in the center? I'm sure it's probably right, but just being a lay person, it seems like the worst place for it. On most chassis' I've seen, the IEC connector is on one side, which means you now have to route it to the centre. Instead of having one poor area of stray magnetic fields, and one good one (if it's to the side), you now get the whole chassis potentially having stray magnetic fields. Also, where do you put the input connectors and speaker connectors? They are sort of equidistant from the toroid on both sides, which seems like they are equally bad now.

Like I said, I suspect there is a good reason for it, but I'm struggling to see it. Thanks.